Kipchoge has been spectacular, winning race after race since 2013. But all good things come to an end.
1. There are a lot of really fast runners out there, not just Kipchoge. Last year, four men ran under 2:03:
2:01:41 Kenenisa Bekele
2:02:37 Eliud Kipchoge
2:02:48 Birhanu Legesse
2:02:55 Mosinet Geremew
Another five ran 2:04:
2:03:16 Mule Wasihun
2:03:34 Getaneh Molla
2:03:36 Sisay Lemma
2:03:40 Herpasa Negasa
Kipchoge is older than all of these men except Bekele. It is reasonable to assume that he will start to slow down soon, whereas some of his competitors will get faster.
2. In the past, Kipchoge has benefited from shoe technology, but he may not enjoy this advantage going forward. For example, he beat Guy Adola in Berlin in 2017 by 14 seconds. If not for his Vaporflys, he may have lost that race. (According to the most recent Letsrun.com podcast, Adola was not wearing Vaporflys.) Presumably, Kipchoge's shoes will be more in line with those of his competitors next year and beyond.
None of this is to take away from Kipchoge's extraordinary accomplishments during the past two decades. He is the GOAT for sure. But the gap between him and the rest of the world is smaller than many people realize.