Fan Zhendong is arguably already better than him. I don't know if he is mentally strong enough to win the big tournaments yet though. ZJK is taking a timeout right now, we will see what he can do if he returns, the old zjk can probably challenge him
I would probably bet a lot of money on FZD becoming the next world Grand Slam Champion, at times he has looked unstoppable. Don't get me wrong though, Ma Long and ZJK can still beat him if they really want to! But this will only last so long... I would include Xu Xin, but he has a poor record against FZD
It would be difficult for one of the other young Chinese players to match FZD as he has had a lot of exposure to high level tournaments and has played in many more pro tour events. His experience is far greater than those of a similar age to himself.
There is always a chance that someone from outside China can become dominant! You never know.