What? Federer is slowly being phased out, and I think Nadal may do also. Fed has struggled to handle the extra power from taller guys like Djokovic and Murray. Sorry but the trend is and will always go up. 185cm being requisite 5 or 6 years ago will be 190cm in a few years. In the 80's you could dominate at like 5'10 or 5'11. It goes up, that's just a fact of life.
I don't know anything about Coric, and maybe he will grow a few inches and be a top player. I'm just saying if you don't have height you must have exceptional talent to compete with the best for GS in the coming years. 6 foot players won't cut it unless you have all world talent like a Federer.
Actually I made mistake. He is almost tall like Ivanišević (who is 1993). He has good serve, trains in London and has his own coach from there.