A bunch of scripts that had been sitting around like next summer's GIJoe
got greenlit because of the writers' strike. A whole bunch of stuff was rushed into production so the writers' strike and possible actors' strike would not effect product flow. I believe Star Trek
and Harry Potter
are just being moved to take advantage of weak competition. Other movies like the afore mentioned GIJoe
are being put in odd spots like August in order to (theoretically) expand the blockbuster season.