I would say that it's possible that they'll be doing soft openings (opening the ride unannounced), but it may only be at certain periods of the day. Before you go on your trip, check out some Disney-related rumors sites (screamscape.com and wdwmagic.com come to mind) - They might be able to give you a guess as to whether it will be open.
On our last trip, on our last day, screamscape.com said they would be doing testing for Mission:Space late in the afternoon around 4:00. So my brothers and I walk over to Mission:Space and wait outside until 4:30. We see activity inside and there were several other people waiting out front. Fortunately, we got to ride Mission:Space the first time it was open to the public. Very exciting!
So, to make a long story short, check out those websites. They were very helpful to us!
RyMickey