The rumored Apple Tablet may turn out to be a kick-butt gaming machine.
A bigger screen, hopefully better battery life, and the iPhone OS would make a great thing (the iPhone/iPod Touch) even better.
A lot of questions remain, however. Presumably, the tablet would have much higher resolution than an iPhone. So, for games, they would have to be rewritten to take advantage of the unique screen.
An iPhone-emulation mode could allow existing games to run in a 320×480 mode scaled up, but that probably wouldn’t look too great.