Obviously Ubisoft were looking at the poor sales of the WiiU and wants this title to generate more income by releasing it on different platforms. That doesn't mean they couldn't have already released it now for the WiiU though, so that part is a bit confusing. I'm not too concerned about Rayman coming out at the same time as GTA V, like Akalabeth said earlier, it's not the same type of game at all. Although GTA V will surely take a lot of time off gamers hands, Rayman is the perfect compliment to play alongside GTA IMO.
If I was a WiiU owner though, this is worrying news indeed. It is another sign that the WiiU is not doing as well as Nintendo hoped it would do, and sign of a 3rd party AGAIN loosing faith in one of their consoles. It happened with the Wii and now it's happening with the WiiU as well. And as for all those supposedly game enhancing features of the WiiU version of the game, I guess these were more gimmicky than UbiSoft would like to admit. I wouldn't be surprised if the PS3/360 versions end up being just as good.
Personally, I see nothing revolutionary about Nintendo's new console/controller. It is gimmicky at best, and very nice to have, not NEED to have. I fear that if I buy the console I will grow tired of it just as quickly as I did with the motion controls of the Wii. Although I thought Skyward Sword was great fun (and I loved the art style), I got fed up with the motion controls, and to date it is the first Zelda I have never got around to finish. When it comes to gaming, I'm perfectly happy with a simple analogue controller and being able to CHILL on the couch, and not worry about which direction I'm pointing with the remote.