How much rating improvement is out there?

[Valen007]

With currently Stockfish and Komodo topping engine rating lists with a whooping CCRL 3340 rating, is there a lot of room for improvement left? Are we going to see 4000 chess playing engine?

I am also curious to whether all strong chess engines use negascout/tree building technique? Are there neural networks in the game? I also read about Monte-Carlo style chess engine.

Best regards,
Valentin