does that mean we have to replay our games to unlock them?

or will there be a way they can check how far we got into the game and just apply it to the trophies?

i would hate to restart my games over just for the trophies.

anyone have any ideas?

Who knows.

I thought that was the main reason for trophies. Re-playability. 

Yes, but you shouldn't HAVE to re-play them.

Nobody knows, thats one of the reasons I didnt go and get all the hard achievements in DMC4, cuz if u had to replay it to get the trophies, i'd be pissed.

Hmm I think they will load your save files and give you trophies based on that;.

I hope we have to replay them, would give me a reason to play the games again(especially GTA 4).

I'm not really sure. I suppose that since most (all?) games keep track of a wide range of stats automatically, it should be possible to read/translate/add trophies for stuff you've already done. Whether devs will do this though, is another matter entirely...

Im guessing it'll depend on the game. Some games like DMC4 appear to have trophy support already and game like Resistance / Rachet and Clank will proberly just transfer skill points to trophies... however for games like Motorstorm - expect a patch ...