From an uncertain future point of view I could understand their concern if the plug was being pulled now but we have VFP 8 in the wings? Shouldn't they be more concerned about investments into things like training or your existing codebase?

For me the argument would be to put a price tag on what investment you currently have with VFP and peoples skill in this area and see whether moving to VB.Net or C# is a palletable option.

Regards
Neil