The Examineris reporting that Season 5 ends on April 5, 2011. That's 14 weeks after the premiere, though Jersey Shore normally only runs 12-13 episodes a season.
If this date is right, it could mean several things. Maybe this is an extended season, with a whole extra episode of drunken Jersey goodness. Maybe there will be a week without a new episode at some point during the season. Or maybe it will be a regular 13 episode season, and April 5 is the date of the reunion show.
At this point it's hard to know, but we'll keep you updated when we hear more.