First off, I appreciate that Kipchoge is still coming back and going after it, even knowing that he is on the decline of his career. Unlike some of this sports stars, its clear that he really loves runnning, and, yes, he still gets paid for it, and probably still handsomely too, but I think he really loves it. Like we do. (Like SML and Mu don't, which I think infuriates most of us because we wouldn't be here, on a running site, discussing it if we didn't.)
So that alone makes him a great ambassador for the sport, which we have sorely lacked. Kipchoge made the "anonymous Kenyan wins another marathon" narrative go away for a while, and it has been a huge benefit to our sport.
Do I think he can still win? I think its very, very clear that he isn't world class on hill courses, so coming back to London makes a lot of sense. I don't think that he can win against the new, younger legs, but will hang with the pack for a while before dropping back. After his DNF in Paris, I could actually see him playing it a bit safer for the first time in his career and dropping back a bit early so that he can hold pace and finish well, even if its in 5th or 6th place, but feel good doing it to banish the memory of Paris. So instead of hanging to a 2:02 pace until 18 and then dropping way back, he could drop off at 7 miles and run solo, pick off some stragglers, but come in feeling good as opposed to defeated again. That's my guess.
Kipchoge brought marathoning world wide attention, having him still in our sport is a good thing.