This thread is strange because it's just two completely separate questions put into one.
Can Grant Fisher, the fastest American distance runner ever, run under 59 minutes in the half? What about 58:30? This is it's own interesting question. American runners historically have a lot of difficulty translating track times to the half and full. Of course with 26:33, Fisher is one of the quickest ever, and looking at Eliud and Kiplimo, his 'ceiling' at the half and full could be 2:01, 57:30 or quicker. But of course it's not so easy to just directly achieve your absolute human ceiling.
Anyways, completely separately, theres Jacob Kiplimo, the absolute most prodigious talent at road running, specifically the half-marathon, we have ever seen. He's broken 58 minutes on three occasions, including a completely solo 57:31 WR. He easily dispatched Aregawi at world XC, who just went on to run 26:3x on the road, again mostly solo in rain if i'm not mistaken. Anyways, for Kiplimo, the question is can he break 57 minutes, and perhaps how close to 56:30 can he get?
These two being in the same race doesn't really mean anything. Going with Kiplimo in a WR setting means opening in 27 flat on the road. It's suicide for almost anyone, but especially Fisher, at least until he shows he has sub 58 in his wheelhouse.