Winning more majors like Boston/NY/Tokyo or another Olympic gold is waste of time for him. He doesn’t need to prove anything there, and it wouldn’t be interesting for anyone (except Americans that for some reasons think that winning the most majors and winning the most Olympic medals regardless of time is the most impressive thing, because “it’s about winning, not about time”). There is zero challenge there for him, it’s boring.
His challenging next possible step could be:
1.retire and go to his wife and kids being a full time father and husband.
2. Trying to go sub2 in Berlin whatever the cost is (even losing the race). Sub2 Monza again isn’t impressive enough due to his new time which might be already equal to sub 2 Monza.
3. Trying to break Bekele’s records in the 5k and 10k on the track.
4. Not that interesting comparing his last achievement - breaking the HM record