A quick scan of the figures
Indicates the numbers we are talking about are relatively small. Around $200m in cuts. That's 1/4 the cost of one shuttle launch (likely a lot less depending on who you're listening to). MSL is $1B+. MERS around $.8B. This is the kind of money that can be easily alloated by OMB after the budget is "decided." And these are thus far merely proposals.
I wouldn't be too worried at this point.