“Shrek Forever After” opened at an underwhelming $71.2 million, even with the second round of ticket price raises so far this year and bloated surcharges for 3-D and/or IMAX at many locations. It way failed to meet expectations of an opening north of $100 million like “Shrek 2” and “Shrek 3,” neither of which had the benefit of stereoscopic and stratospheric ticket prices approaching $20. So if there’s a “Shrek 5,” I’m betting it will probably go direct to video. Spinoffs anyone? “Iron Man 2” dropped 49 perent to second place for $26.6M for its third weekend, while “Robin Hood” dropped 48 percent to $18.7M for $66M domestic so far — not too shabby for a film that is doing blockbuster numbers overseas, the market for which it was primarily designed.