To date in the 2009 season of Major League baseball, 46 grand slams have been hit in 1,116 games played by the 30 major league teams. At this rate [(46/1116)=(x/4860)] where 4,860 is the number of games played overall in one season (not including postseason play), players will hit 200 grand slams by the end of the regular season play. That breaks the old record for total GS's in a season by 24 grand slams.
Stay tuned to see if it happens or if the frequency dies out. If it does happen, I predict Manny Ramirez of the Dodgers to hit #177.