Short answer for me -- if someone offered me 30-1 odds on Rupp medaling, sure I'd bet $10 on it... but probably not much more than that. The race would be a lot more fun to watch too.
Looking at the past 4 world championships/Olympics, the slowest anyone has run for the season and medaled is 27:22 (Tadesse in Athens).
On a side note... in looking at these results, I can't imagine how Sihene hasn't gone Tanya Harding on Bekele yet.
(season's best in brackets if lower than championship performance)
2008 Olympics 10K Final
1 Kenenisa Bekele ETH 27:01.17 (OR) [26:26]
2 Sileshi Sihine ETH 27:02.77 . [26:50]
3 Micah Kogo KEN 27:04.11 (SB)
4 Moses Ndiema Masai KEN 27:04.11 (SB)
5 Zersenay Tadese ERI 27:05.11
2007 World Champs 10K Final
1 Kenenisa Bekele ETH 27:05.90 (SB) [26:46]
2 Sileshi Sihine ETH 27:09.03 . [26:49]
3 Martin Irungu Mathathi KEN 27:12.17 . [27:10]
4 Zersenay Tadese ERI 27:21.37 . [27:00]
5 Josephat Muchiri Ndambiri KEN 27:31.41 [27:28]
2005 World Champs 10K Final
1 Kenenisa Bekele ETH 27:08.33 . [26:17]
2 Sileshi Sihine ETH 27:08.87 . [26:57]
3 Moses Mosop KEN 27:08.96 (PB)
4 Boniface Toroitich Kiprop UGA 27:10.98 (SB)
5 Martin Irungu Mathathi KEN 27:12.51 [27:08]
2004 Olympics 10K Final
1 Kenenisa Bekele ETH 27:05.10 (OR) [26:20]
2 Sileshi Sihine ETH 27:09.39 . [26:39]
3 Zersenay Tadese ERI 27:22.57 (NR)
4 Boniface Toroitich Kiprop UGA 27:25.48 (SB) [27:04]
5 Haile Gebrselassie ETH 27:27.70 [26:41]