According to the cheatcc podcast R* will be going PS3/PSP exclusive. All upcoming titles other than those in production will be on the PS3 only. If this is true it could be a huge coup for Sony as it measn that all the GTA IV spin offs will be PS3 exclusive.
http://www.n4g.com/industrynews/News-57037.aspx
I find this a bit hard to believe but the guys in the podcast seem to think it will happen.