As I understand it, it means all uniformed American (Military) employees will be dispersed to other locations (which can be recalled in 24-48 hours for Fairford to be activated). The base will now be maintained by the remaining non-uniform (Civilian - Mainly British) employees. However up to 100 civilians will sadly also loose their jobs as part of this cut.
As Wrathmonk says, the activation time isn't much longer than the current time.
Fairford will remain the host to RIAT and also Deployed Operations Training Exercise.
Mike