Little early on that one given that Hamilton is still 2 years away. Guys have started out hotter and fallen quickly than Cozart who were much more highly touted. Not that I expect it to happen, but Cozart has what, 100 at bats in his MLB career?
Cozart is 26. His game is mature. He is not going to fall off a cliff.
The best argument for keeping Hamilton and Didi at SS is build trade value. It could very well be the best way to go.
However, SS is not a position of need -- it's the opposite. CF, on the other hand, is looking weaker by the day. Lotta toolsy players who, with the exception of Phipps, have never shown a level of performance that matches the tools. Hamilton would instantly become the top prospect at the spot with no apparent roadblocks, IMO.