They already have haptic feedback on their trackpad, which is non mechanical. Merging the touchbar and trackpad would make a lot of sense; it's a lot of real estate to waste. Oled is the way to go here though. That's what they did with the touchbar.
It would take me a while to get used to having to press a button to show the trackpad like on the Yoga Book. I like that it automatically hides when typing, but constantly having to bring it back up, to scroll in a small textarea for example, would be annoying.
Merging the touchbar and trackpad, kind of like that Asus laptop that came out recently would be interesting. I thought it would be awkward at first but a lot of reviewers seem to think it's useful.