Here is a list of the 12 fastest 10k runners over the last three years with their best 5k time in that period (note that most of these times are two years old, I suspect that the Olympics being last year kept times a little slower.):
12:49.53 Kenenisa Bekele ETH 28/07/2007
12:50.16 Sileshi Sihine ETH 14/09/2007
12:50.38 Eliud Kipchoge KEN 14/09/2007
12:50.55 Moses Ndiema Masai KEN 01/06/2008
12:50.72 Moses Ndiema Kipsiro UGA 14/09/2007
12:51.00 Joseph Ebuya KEN 14/09/2007
12:51.95 Thomas Pkemei Longosiwa KEN 14/09/2007
12:52.45 Tariku Bekele ETH 01/06/2008
12:55.03 Edwin Cheruiyot Soi KEN 28/08/2009
12:56.27 Dathan Ritzenhein USA 28/08/2009
12:57.56 Abreham Cherkos ETH 01/06/2008
12:58.49 Yusuf Kibet Biwott KEN 14/09/20077