Sheppard was cut some by BRAC in 2005. I think the general feeling is Sheppard is probably safe until at least 2015. Rumors of a 2013 BRAC have surfaced, but I have not seen or heard of anything in the budget for a 2013 round of BRAC, and closing bases costs money, so that would have to come from somewhere. A 2015 round of BRAC is more realistic.
I've seen comments from Thornberry and others that think because of the NATO training program, Sheppard is probably safe from BRAC in the near future.
Personally, I'm not as optimistic. If there is a change in the administration, it will be safe for a while. If not, being from a relatively small metro area in a Republican-dominated state could very easily bump it way up the list.