You really think Rupp is going to break 59:43? Why would he even try to do that now that he's a full time marathoner? I can't imagine him doing this, but you never know I guess.
I know some things wrote:
I'm going to go out on a limb and say that Galen will beat Hall's PRs at both marathon and half marathon and finish his career with ARs in 10k, half marathon, marathon.
It is no contest.
I can't find the link, but I remember someone looking into when elite marathoners typically set their PR, and I seem to remember that it was right around the 3rd race. The number of marathoners who suddenly PR a few years into it is surprisingly rare. Rupp hasn't run in a particularly fast race yet, so maybe he'll be the exception, but the notion that a 2:06 is just out there waiting for him seems a little naive (especially as he ages...)