Would you as the CEO of a videogame corporation approve a PS3 game now knowing that in about half a year there will be a new, far more powerful machine available?
I would. That new powerful machine is only going to have a potential 10-20 million customers as opposed to 75+ million for the current gen systems. If anything I'd develop a new game for PS3/Xbox and just gussy it up to 1080P and 3D or whatever for the next gen systems. Usually we have at least two years of games still being released for a generation after the next gen starts.