Based on the lastest update on the Status of Entries page on USATF.org, it looks like they are sticking with 24 for the men's 5k. Two prelims of 12 each, to a final with 16 people (I am assuming 16, since that is what they did in 2004).
There were only 28 declared. Kinda sucks for those 4 guys, but at the same time, they likely would not have been factors. But it does seem a little odd that 16 are OK for the final, but 14 are too many for a prelim?