There are at least two movies coming out this summer with elements of time travel and alternate universes.
Due out May 21st is Shrek Forever After, the fourth installment in the franchise. This go around finds Shrek doing battle with Rumpelstiltskin who tricks him into wishing for a universe where he never met Fiona and still lives in the swamp. This alternate universe has Rumpelstiltskin as King and Shrek is forced to try to set things right.
Due out May 28th is Prince of Persia: Sands of Time which is based on the video game of the same name. Starring a very buff Jake Gyllenhaal, as the Prince Dastan who is trying to stop the Sands of Time from destroying the world. The Prince is able to control the flow of time using a magical dagger.