I think you wait until the rest of his teammates are gone. It wouldnt feel right to be watching Morris (hopefully), Naz, and Thomas out there for a game with Georges getting his jersey hung. With the number of upperclassmen on this team I think you could do it the year after next at the earliest.
Some of it may also depend on his pro career. To me, it's something you do when their basketball career is over, but if he looks to be able to have a long NBA career then I don't think you wait that long. If he fizzles out in 2-3 years I think you do it shortly after that.