Actually, the GP2X is already capable of emulating PS1 games (and it does it pretty well), so it shouldn't be much of a stretch to see an emulator being ported and shipping with something like this.
GP2X capable of emulating PS1 games? Yep, sure can. Does it pretty well? Uh... I wouldn't think so. The PS1 emulator is an impressive bit of software engineering to get it to where it is, but given its best results thus far are "barely playable", it'd be a claim of great temerity to say it "does it pretty well". Still, your standards could well be lower than mine, so if you're happy/happier with it, then more power to you.
Back to the original point though: a PS1 emulator on the Pandora is a lock-in. A dead certainty. And I'm sure it'll run well enough that people will buy the Pandora just for that. But even in the unlikely event that a PS1 emulator for the Pandora ships with the machine, it's still gonna need a PlayStation BIOS to run it, and CDs encoded into rom files to play on it. All do-able, of course (with varying degrees of legality), but anyone considering that as "PsOne emulation 'out of the box'" is in for a world of pain.