Will there be a way to use the usb host (possibly the tv out cable) as tv in? For example, say I wanted to use my gp2x as simply a monitor and pair of speakers for something else like a dvd player or xbox. Will this be possible?
Yeah, if you had a USB tv capture board, like something from Hauppauge (they have a USB WinTV model) you should be able to do it. The drivers should exist for Linux (thanks to all of the digital PVR folks!), though I'm not sure if they'll be for kernel 2.4 or 2.6 only... they may need back-porting.