It depends on how exactly one defines porting. Personally, if Sega wraps up their Megadrive games into a standalone emulator that runs out of the box on a PC, that's already a port in my book. Not a native port, but still a port. Of course by your definition it wouldn't count as a port. So who is right? I don't know and personally I don't really care as long as the game runs properly :P It would certainly help to specify what type of porting one means when talking about ports (native, Wine, emulated, etc.)
Few87: So from what you say it does sound like gog may indeed port more games over to mac.
Well, you shouldn't count on it. What I meant is that the technology is there, however the question is if they can do it in a way that would be feasible. They would have to be able to test such a port on many systems and they would have to be able to provide proper support. What works for one person does not have to work for another. You can count on seeing the DOS games ported, but for Windows games your best chance is if there is an official Mac version by the developer. On the other hand, GoG have already annouced that they will bring over all of the remaining Interplay titles in time, so I'm not ruling Wine ports out completely. We'll see what happens.