25...
Haha. One of my games is on 11 or 12 disks, I think it maybe was Monkey Island 2. It's funny to hear new generation gamers think of disk swapping as a problem.
But to be honest it is a pain to swap disks often, it's just that we've not been so used to it after discs (optical) replaced disks.
I have no idea but I just guess GTA5 will be on more than one disc.