They Can't Re do Khan!
Apart from the fact it is a rubbish idea and I really don't want to see a rehash of a perfectly good movie (not that that has ever stopped Hollywood). TWOK is set much later than the 5 year mission so either they would have to make Space Seed into a movie or they would have to age the crew considerably.
Besides, the fact that they all got together on the Enterprise together in a different way than in TOS canon, this means that the Five Year Mission is an entirely different mission - if it happens at all. So they might never meet Khan.
"Unless you have something a little bigger in your torpedo tubes, I'm not turning around!"