Lets face it, there are only 3 perspectives in this debate, and here they are stripped down to what they really are:
Kingdom Hearts is a Sony exclusive, (portable versions don't count) so it will ALWAYS be a Sony exclusive. We'll finally see Kingdom Hearts with Advent Children level graphics! The creator loves the PS3, so it's sure to stay there, make up for PS3 losing FFXIII exclusivity to 360, and launch the PS3 into the glory it deserves!
All characters in Kingdom Hearts except for characters from existing Final Fantasy games are owned by Disney, so Disney can decide what system Kingdom hearts can go on. Disney loves money, and has the same type of nostalgia/family friendly recognition that Nintendo, and specifically the Wii, are also currently known for. With the incontestable domination of sales for the Wii and Nintendo in general, as well as the comparatively low sales of the Sony Platform, there's no way that Kingdom Hearts won't be moved to being a Wii exclusive. Also I'm not interested enough games on the other consoles to be worth getting them, so I'd end up missing out on a game I really like. Oh, and maybe Square Enix will use the opportunity to bring Geno back!
Kingdom Hearts is obviously going to come to the PS3, since it got its start on the PS2, and is certainly going to take advantage of the HD graphics. Sales for the PS3 aren't good enough to make it profitable, so it will certainly be yet another game that is ported to the 360 in order to capitalize on Europe's and Japan's PS3 domination as well as USAs 360 domination. Of course, since it will be in HD, there's no way it will be on the Wii.
Personally, the longer it goes, the more convinced I am that it will go towards the Wii. Wii can handle better graphics than the PS2 and Kingdom Hearts has a graphical style that doesn't really need to be updated that significantly. It's also only a few million away from overtaking the combined PS3 and 360 sales worldwide, which I'm pretty much certain is going to happen before the end of next year. There has already been a Kingdom Hearts game on the GBA which included Final Fantasy characters, and it's also being continued onto the DS. So the issue of final Fantasy characters not appearing on a Nintendo console are likely a moot point.
Basically, my bet is that if my sig is true, Kingdom Hearts will be designed primarily for the Wii, if not ending up as a complete exclusive.