The original Wii portal and software are 100% compatable with Wii U. All Wii accessories, controllers, and games will work on the Wii U. The skylanders will retain their stats and work on any platform. The portal owner's pack is not a very good deal on any platform anyhow. It makes more sense to spend $15 more for the starter pack because you get an additional 2 new skylanders and a portal. The extra skylanders are worth $20 by themselves.
Wow. Considering Amazon's current prices for either the starter OR the portal owner's pack are the same (except for the Wii, curiously, which is still about List Price), there's really no need to worry about that. Though it would have made sense to assume that a Wii U owner MIGHT have also been a Wii owner and already had the portal, so making an owner's pack available isn't incomprehensible.
It is my understanding that the Wii portal is not compatable with the Wii U software. Also, the Wii U portal is corded (like the xbox version) most likely for a reason. I suppose the Wii owner's pack would work, but then you won't be able to play on the Wii U control pad, and would be 480p at best. Again, not worth the few bucks you would save.
Both portals are compatible with both games/systems. We've been switching back and forth between them to build up stats and gold in the old game while playing the levels in the new. The ability to play the Giants game entirely on the Gamepad makes that pretty cool. And as it turned out, I was able to grab the Wii U starter pack for $15 less than list and return the Wii version we'd purchased earlier from another toy store's online site. We missed out on a free Legendary Drill Sergeant, but it wasn't a Series 2 figure, so no big loss.
Appoligies A. Stefaniak. Apparently I was misinformed by a big box employee (again). Why can't they just say "I donno"? Still, at the the time I write this, the price gap between starter and owner's packs (the other consoles) has dropped to 5 bucks making even less sense than before. I can't figure Activision's marketing on this. I suspect a price drop on owner's versions soon due to lack of sales.