Couple of thoughts on this...
First, Mission:Space is already going to be postponed, I'll bet. Rumors I've read on other sites seem to indicate the ride will not be ready until at least this summer. M:S is a highly technical ride, much like Test Track, and I'm sure its opening will be delayed.
Second, Disney could do something very nice, and dedicate this attraction to the Columbia crew, perhaps include a memorial to all those who have died in the pursuit of spaceflight (if one is not already included in the pavillion somewhere). The ride itself could easily be modified to remove any unpleasant elements, like a simulated malfunction, etc.
Third, Disney isn't in the financial position that would allow it to sit on a very expensive E-ticket ride. Epecially in Epcot, where attendance is flagging, and the so-called Project Gemini has been greenlighted in an attempt to raise the appeal of the park. You can bet that they won't delay a moment in turning this ride loose once it's ready.