deelee74: i wouldn't count on it really. gog is great OLD games, and old games for the mac will not run on modern macs. Any game made for a Mac Pre-OS-X will not run on an intel-based mac, and OS-X games that were made for g3 and g4 processors often won't run fast enough in rosetta to be playable.
The mac is becoming a great native platform for games, but for your GOG's, the best bet is to get Dosbox for the mac and to grab a copy of Windows XP and use bootcamp.
Actually I've found Wine to be compatible with especially a lot of older Windows games these days (minus an annoying problem in OSX with joystick compatibility) - though I have a boot camp partition just in case ... :)
But that is in general a fair point, games of classic OS 9 or earlier are not going to work in OS X without major rewrites and Apple is even moving away from supporting non-intel programs - so Rosetta will go away in OS X Lion, at least support for it will go away, maybe you'll still be able to have it - so again, major program program re-writes.