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.
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 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...)