all the top 4 guys all time could run sub 140.
coe's 141, that was sub optimal conditions, pacing track surface.
the other 140 141 runs were front run, or with very dodgy pacing, like 23flat for the first 200, uneven pace, tracks could have been better.
no question. i think coe said himself he could do 139.
rusd 140 front run, that is only 8 meters off 139.9
coach of john walker, arch jelley, wondered why someone did not pop up and do it, back when the record was 143. by a guy that set that mark in his first season doing it, and broke down not too far after.
right now, there are no athletes that can run a 141 with a suboptimal situation, so 139 is out of the question currently.
the guy to do it, will be 45 low 400 m or very close to, which all the top 4 all time were capable of, no doubt. you don't get your best 400 time on the books using it as sharpening, while doing mileage... of course,
a guy like garth bale of notable endurance and the fastest player, that type of guy would be next level.
remember, you only do track and field when something goes wrong in other sports.
which means it is a fluke to get a super talent in this sport.