It will be interesting to see what he does for sure.
I loved IMDN and wasn't sure he could top that, and he did with JP, which I think is one of the bear pins of all time...maybe the GOAT.
I think creatively, it's hard to stay fresh and unique. I can't imagine how difficult it is for Richie and Borg, who've designed so many games.
I do hope Keith has the juice/goodwill/trust/freedom to do what he wants. He's clearly massively talented. I love that he does the rulesets as well...it just makes for such a cohesive/integrated experience in my opinion.
I also hope he continues to make challenging games like JP. Most games are going in the home and played by experienced players and tournament players likely prefer the challenge as well. Stern puts out plenty of games by other designers that are easy to shoot.