Actually Dmitri Aliev is trying to do the 4A. He has not yet been successful. I don't think his 3A is even very good so chances of 4A seem rather dim but soldier on. The sport always moves forward. I believe there may be others too. NC has even been seen trying it. I remember seeing in old videos Kurt Browning, I believe, jumped the 1st quad in competition years ago and it wasn't as neatly done as they do today. Others had done quads but I think his was the first in competition. Correct me if I'm wrong. Anyway technique improves with time.
But I concur. Now is Yuzu's time. I believe he can achieve 4A, it just has to be ratified to be in the books. Yuzu won't be satisfied if it isn't +GOE so I know that is what he will strive for. He always strives for perfection. For me, I am happy that he always pushes forward to lift the sport. He has already changed FS forever. I want him to be satisfied so that means 4A but he will always be legend regardless. There will never be another like him. Ganbatte, Yuzu! Fly!