“The Avengers” (May 4) Summer officially begins right here, with Joss Whedon’s overload of superstar superheroes. Iron Man (Robert Downey Jr.), Captain America (Chris Evans), Thor (Chris Hemsworth), The Hulk (Mark Ruffalo), Hawkeye (Jeremy Renner) and Black Widow (Scarlett Johansson) join forces with Nick Fury (Samuel L. Jackson), to defeat any and all box office records. Oh, and Tom Hiddleston’s villainous Loki. The Bottom Line: Between this and the fanboy fave “Cabin in the Woods,” Whedon can expect to end 2012 as a cineplex superher o himself. E.W. “A Little Bit of Heaven” (May 4) To judge from the trailer, Kate Hudson’s latest date flick isn’t much different from the ones that came before it, except that instead of planning a wedding or searching for treasure, she’s battling cancer and Gael Garcia Bernal helps her find true love. The Bottom Line: It will be on your cable box the same day it’s in theaters, which isn’t a great sign. Even if this effort proves the exception to her recent disappointments, it’s time for Hudson to rethink her career. E.W. “Dark Shadows” (May 11) The cult vampire soap of the Nixon years rises again, thanks to director Tim Burton and his…