Obviously, I think all of these are unlikely to be broken for a long time, although you never know...
But if I had to pick, in order of most likely to least likely:
5,000
10,000
800
Mile
It was a hard pick between 5 and 10, but I went with the 5 just because it’s run more often. I think there are a few guys that can run under 12:40 (5 or so, without counting), which is an increase from 2-3 years ago so if the influx keeps up, it’s possible one of them could break 12:30? Again unlikely but still the most likely of the choices.
The 10 has Kamworer, Cheptegei, and Kipruto, all capable of running under the current WR but breaking 26 would be insane. But who knows, if one of them really goes for it and somehow doesn’t get popped...
800m Brazier is a freak, but I’ll still be surprised if he breaks 1:40.... and no one else is even close. When barely anyone comes within 2 seconds of that barrier I can’t see it happening.
The mile, as others have said, is equal to about a 3:25 1500. Cheruiyot hasn’t even broken 3:28, and nobody else even broke 3:30 last year (going off memory so I could be wrong here). This is not happening.