Ok Well according to Safari Steve the ride may very well be opening around may/june (I believe that is what he said). But according to David Koenig's MousePlanet artical the ride is behind schedule:
"Don't expect Epcot's newest attraction, Mission:Space, to open any time
soon. Imagineering had hoped to open the thrill ride this spring, but
construction has fallen behind schedule (although apparently not 'Test
Track-level' behind schedule). The new target date for soft openings is
late summer (end of August) at the absolute earliest."