It looks like the first film is finally getting a much needed remaster for this set. All I can say is it's about time. I don't think any of the other films are being remastered, but I can live with that.
The new set is going to have the 4k restoration of Rocky, and the rest are going to be the existing discs. So if you have the previous set, then buy the new release of Rocky and replace it in the Undisputed set. No need to buy the whole thing again until they restore the rest of the films, which probably won't be happening at any point in the near future.
This set includes the same versions of "Rocky II-V" and "Rocky Balboa" previously released in the "Rocky Undisputed Collection". The seventh disc of extras from the "Undisputed Collection" has now been added to the disc containing the original "Rocky", and three commentaries from the "Rocky" DVD have been restored. "Rocky" has also been given an improved video presentation.