Since when does square even make multiplatform games? 

Games shouldn't even use CG anymore, but the CG on the PS2 games were crap. Mickey and Goofy looked like crap because the graphics were too good they looked computer animated (well they are, but they shouldn't look like it). CG was good in the PS1 days, now we move toward real time cutscenes.

bunch of bs. most of the fanbase of the ps2 hasnt switched to the ps3 yet. by the time they release the game the ps3 instal base should be fairly large and most of the people who bought the game for ps2 will have bought a ps3.

well that's a nice assumption you have that all the PS2 fanbase will all buy the ps3.

Even though there is a lot of truth and sense in what you just said, i'm sure by the time KH3 does come out, PS3 sales still won't be near Wii sales. And like Soriku said, i'm sure the 100 or so million people who still have PS2 aren't just going to buy PS3's overnight. The price can't drop much farther without Sony losing massive amounts of money.

i did not say the entire 120 milion ppl will buy ps3's. all i said was that most people who bought KH1 and 2 for Ps2 will have a PS3 by the time the next one is released, so the sales of it will be about equal. i dont know the exact number of ppl that bought it ww, but im am assuming it is around 4-5 million. And ww the PS3 already has aprox 4.5mil. is it that farfetched to think by the time kh3 comes out (prob 2-2.5 years) the instal base will go up by at least double? i think not. so bottom line. it would do fine on the PS3 because by the time the next instalment is released MUCH (not all) of the ps2 gamers will have moved to the PS3.

I didn't know that 100 Million people wanted a PS3, or maybe they're not all brand loyaltists and want a 360/Wii.

There is not a chance in hell it will sell 5 million on a 15 Million userbase. Few games in existence had a 33% attach ratio. And it isn't coming out on the PS3 for very, very, obvious reasons.

and just because Wii has a bigger instal base then PS3 doesnt mean it will sell as well. look at madden 08. in NA the wii instal base is much bigger then the PS3, but the PS3 killed it in first week sales. Im not saying it is true for kh3, but S-E has probably thought about how much the wii is more of a first party system.

You are assuming "MUCH of the ps2 gamers will move to PS3."  If you look at the thread "question for wii owners" most of the current Wii owners were PS2 owners.  The thing about the PS2 is that everyone bought it last gen, how could you not?  Even if you were a Nintendo, Microsoft, or Sega fanboy you pretty much had to buy the PS2.  It's also wrong to assume that all the people that bought KH will automatically buy a PS3 because the game went to it.