I think 4K in a Macbook is a bit too far... the higher the resolution you cram into a small screen, the lesser the benefit. I mean, look at phones. Samsung has had 1440p screens since the S6, but iPhones stayed with 720p and 1080p, with screens that still looked sharp.

Here are the features I would like to see in a Macbook Pro:

1. Micro-LED for the 15" model, and Super-IPS for the 13" to reduce costs without too much of a drawback (like on the iPhone XR)
2. A more powerful GPU (perhaps Nvidia's Max-Q designs?) on the 15", and a larger battery (I wouldn't mind a larger battery at the trade-off of a bit more thickness, like the 2015 Pros.
3. Taptic engine used for keyboards without moving parts (like the home buttons on the iPhone 8 and 7), or at least a switch back to scissor style keyboards

Here are the features I'd like to see in the Air/Macbook:

1. Micro-LED/Super-IPS displays
2. Taptic engine used for keyboards
3. An OS closer to iOS, to eventually make the move away from Mac OS X
4. Apple's own SOC powering the device instead of Intel solutions

Oh, and a more comfortable Magic Mouse.