I'm guessing this is the magazine you were refering to when you heard this info was supposedly confirmed.
http://sd.cubicnetwork.net/images/EGM.jpg (Image provided by Sora's Domain.)
There are however a few things I would like to point out.
The only thing quoted after Nomura is when it says "To me, Kingdom Hearts2 is like a monster-but in a good way," "The game is just so huge." "more than just a means of transportation...it's equivalent to being on a ride at a Disney amusement park." That confirms nothing of what many are trying to say; And when the artical states that the setting on the story takes place one year after CoM this is somewhat wrong. The following Q & A comes from the KHCoM Ultimania guide book interview.
Q: At the end of the previous installment, KH, there was a secret movie that was to bring light on what the sequels could be like. When you made those sequences, did you already have in mind what CoM and KHII would be like?
A: In a kind of vague way yes. The most precise visions I hade were those of KHII as I already had decided that it would take place a year after KH, that the atmosphere would be different in some ways. If I was to create a KHII I wanted it to begin in the most intriguing way as it would be possible. I only began thinking about "What happens in that year between" in CoM much later.
It takes place a year after KH not CoM. CoM holds the events in that year between KH and KH2. There's one mistake the author of this artical made.
In the artical it also says that the game includes areas based on Steamboat Willie, The Lion King, and Lilo and Stitch. Which implies that they will not be the same as the original movies. There will be slight differences in the looks and story. This is of coures if they are actual worlds in the game. I say if because the fact that this is not Nomura quoted and the fact that they lack visual evidence to further support that fact. So until we see screenshots or here word from Nomura, or Wada in an interview we can not finallize the fact that they will be worlds in the game. We can only assume that they will be. The rest of the artical we have proof of so you can take it however you desire.
Also I would like to point out that at the top left it says, "Opinionated guide" Which means that this is based off of there own opinions.