I've yet to see a PS3 in the States not run a PS2 game or PSX game they tried, even in the new consoles purchased this past month. I don't think the Emotion Engineless ones are out here, just Europe. If that is the case, it's more compelling to9 buy now rather than later.
One title that's online only out of a lot isn't cause for alarm. I would hardly call 'Warhawk' the nail in the single player coffin. If Halo, MGS, Grand Theft Auto, Street Fighter, and such all went multiplayer only, then i'd worry.