WD Released these updated versions of the Ultra's 500GB, 1TB , 2TB, and a new 3TB. (For the 2TB The old version was Model # WDBMWV0020BBK-NESN and new version is Model # WDBBKD0020BBK-NESN)
I researched if there are any differences, so here is what I came up with...

Pros
Overall Size of new model is a tiny bit smaller ( see picture for comparison of dimensions on each new model vs old model )
Higher Capacity Available - Now Up to 3TB vs the older model only up to 2TB capacity
Optional 256-bit AES hardware encryption
Now available in white

Same as Old Model Nothing Changed
Weight is the same exact at 0.50 lbs ( 0.23 kg )
Automatic local and cloud backup
Comes in 4 colors ( they still offer black, and blue, red became berry and they replaced titanium for white on the newer models)
USB 3.0 connectivity
Formatted for Windows, reformatting required for Mac
3-year limited warranty
Same Data transfer rate and Operating temperature
USB 3.0 up to 5 Gb/s (max) / USB 2.0 up to 480 Mb/s (max)
Operating temperature: 5°C to 35°C / Non-op. temperature: –20°C to 65°C

Cons
None so far .....

Bottom Line - They are pretty similar so get what is cheaper, unless you need/buy the 3TB they never had one before

New Model WDBBKD0020BBK-NESN
Old Model WDBMWV0020BBK-NESN

7/7/16 Update:
WD just released a brand new 4TB capacity of this drive on 6/28/16. It is essentially the same as the 2TB & 3TB versions of this drive, with additional capacity. It is the same size at 4.33 in x 0.83 in x 3.21 in, and same weight at 0.50 lbs. Offers the same 3 year warranty and will be available in the same 4 colors Classic Black, Brilliant White, Noble Blue, Wild Berry, (a new 5th color Festive Red expected to be released soon).

This model is the 2015 generation of the many My Passport drives I've owned or purchased for clients. They have proven reliable and good performers. They have incrementally improved with each new generation.

BOTTOM LINE (for the impatient):
The new model is a little bit faster than last year's and adds a 3TB and 4TB model. This My Passport Ultra has a more attractive satiny finish and there is now a white model to fit in better for Mac users. Otherwise it's almost identical to the older model.

If these differences are not important for you, you may want to get this or last year's My Passport Ultra depending on which is least expensive. You'll have an excellent drive in either case.

NOTE: As of Oct. 10th there is a new 2016 model with (in my opinion) a less attractive case, but slightly faster drive inside. Otherwise they are similar.

If you want more details, read on...

SUMMARY:
The My Passport USB 3.0 drives are simple to use and come with reasonable software tools and backup/sync software. There are Mac versions of WD tools on this drive as well as the Windows tools. The newer software can also be downloaded for older models. I don't use this software, but plenty of people do as basic backup and/or sync with your WD MyPassport.

Pluses:
+ This drive works fine with Linux or Mac out of the box. It performs best when reformatted with a native file system for the respective operating system.
+ This generation adds a 3TB model to the 500GB, 1TB and 2TB sizes in previous versions.
+ This drive is faster than the last generation. Up to 25% faster in benchmarks, but just noticeable in practical use.
+ The form factor of the new drive is almost exactly the same as before and they have a nice satin like finish.
+ The titanium color has been replaced by a white color (never liked the titanium color)

Minuses:
- It comes with the same very short USB 3.0 cable as previous versions.I like a longer 3ft (or more) USB 3.0 cable: a very good upgrade purchase for the My Passport drives.
- There is no drawstring pouch with this generation of My Passport Ultra drives. Some protection for toting drives around.

IN THE BOX:
The My Passport comes in a easy to open retail package containing the drive and a annoyingly short USB 3.0 cable. That's it. The cable in this model is the same as previous versions. This may be just fine for a lot of folks but I keep some 3ft (or more) USB 3.0 cables handy for longer runs to my desktop or even on top of a tall computer.

FORM FACTOR vs PREVIOUS GENERATION:

I'll compare the new generation of My Passport Ultra with a My Passport Slim (a repackaged version of last year's My Passport Ultra).

This My Passport Ultra's dimensions:
500GB: 0.32lb, 4.33in X 0.62in X 3.21in
1TB: 0.34lb, 4.33in X 0.62in X 3.21in
2TB-4TB: 0.50lb, 4.33in X 0.83in X 3.21in

Last year's My Passport Ultra's dimensions:
500GB: 0.30lb, 4.33in X 0.50in X 3.21in
1TB: 0.34lb, 4.35in X 0.61in X 3.23in
2TB: 0.50lb, 4.35in X 0.82in X 3.23in

TESTING:
I tested both my older My Passport slim 1TB drive and the new My Passport 2TB model using CrystalDiskMark benchmark software and by copying 11GB folder of updates and files to the drive. This was to compare the benchmark with real-world copying. The 11GB folder has a broad mix of file sizes and types including files over 2GB iso DVD images.

Using CrystalDiskMark I found sequential reads were about 25% faster and writes about 10% faster with the new model. Random reads were just a tiny bit faster, but writes were about 25% faster. While the benchmarks showed significant differences in practical use the difference was noticeable but not great.

For my testing the My Passport drive was connected to the Renasas USB 3.0 chip set on my Dell Precision E6500 laptop. I have the latest Renasas drivers installed. The laptop also has a Samsung EVO SSD as the hard drive (matters for my real-world copy testing).

CRYSTALDISKMARK Results:
The New Generation My Passport:
Sequential Read: 112.750 MB/s
Sequential Write: 72.353 MB/s
Random Read: 4KiB 0.584 MB/s [ 142.6 IOPS]
Random Write: 4KiB 1.373 MB/s [ 335.2 IOPS]
Sequential Read: 110.736 MB/s
Sequential Write: 70.680 MB/s
Random Read: 4KiB 0.522 MB/s [ 127.4 IOPS]
Random Write: 4KiB 1.340 MB/s [ 327.1 IOPS]

The Older My Passport Slim:
Sequential Read: 79.434 MB/s
Sequential Write: 63.436 MB/s
Random Read: 4KiB 0.525 MB/s [128.2 IOPS]
Random Write: 4KiB 0.941 MB/s [229.7 IOPS]
Sequential Read: 78.850 MB/s
Sequential Write: 63.329 MB/s
Random Read: 4KiB 0.493 MB/s [120.4 IOPS]
Random Write: 4KiB 0.861 MB/s [210.2 IOPS]

REAL WORLD COPY:
In my real world copy test the new My Passport Ultra drive was just noticeably faster than the older. It peaked out at about 60MB/s with large files. I never dropped below 29MB/s even with large amounts of small files being copied to the drive. The older My Passport Slim peaked out at about 55MB/s and dropped several times to just above 25MB/s.

I'm thinking the newer drive may have a larger on-drive write cache or maybe it's just a bit faster drive. Maybe both. On big copies the new My Passport Ultra may save you a few seconds here or there but your last generation My Passport Ultra drives are pretty close.

CONCLUSIONS:
The My Passport line of drives from Western Digital has been very good to me and to my clients. This reliable and good to excellent performing line has a long positive history with me.

This WD My Passport Ultra is an evolution over the last generation. I'll pick it for new purchases over the older model, but won't rush out to replace older drives. It's a 5 star successor to a 5 star predecessor and continues to be a very good external storage choice.

For making improvements and not messing up something that has been working well for a long time This new generation of My Passport Ultra drives is worth 5 stars in my opinion..

Hope this helps someone!