According to Carmack in this video, Sony will not allow 3rd parties to release late ports of 360 games unless they improve the game in some way.
While I understand the reason, this surprised me a lot. It's interesting in a number of ways - the gamer's perspective, the business perspective, and, most of all, it showed me that Sony isn't as friendly to developers as I thought; I thought they were the most developer-friendly of the three, but I'm starting to doubt that.
My Mario Kart Wii friend code: 2707-1866-0957