The 2015 design literally needs no improvement. It's weight is fine, its thickness is fantastic (still allows for fullsize ports), it has a MagSafe, and a great keyboard. I think the only thing I could possibly look for improvement on is a slight shrinking of the bezel. A 15" is just a tad too big to work comfortably on an airplane.
I had a new MBP for my job and could not stand the thing. It was a terrible experience. I ended up having to get an external keyboard because my finger joints were hurting from typing on the keys, the touchbar was utterly useless, the touchpad was too large for it's own good (and constantly failed to do palm rejection) and the lack of Magsafe was terribly inconvenient.