Moving away from Java, to a combination of C++ and a dedicated rendering engine (Unreal, etc.) would allow the game to break some serious performance barriers, enable cubic chunks (or equivalent), and dramatically improve rendering times, reduce lag and utilize GPUs better. Infinite height, insanely far rendering distances, and improved creature AI.
Shoving it all in Java classes is nuts. It is like trying to fill a beercan with a firehose. Even the math processing in Java is limited.
The reality is that Microsoft will probably recode the thing from scratch at some point anyway, as they slowly push out the old Mojangsters, and I would bet it is considering it right now. But I wouldn't expect to see that version for 3-4 years.
I usually hate Microsoft, but they would do Minecraft some serious justice doing that.