Wow, the 71% weekend drop-off is higher than the massive 69% drop-off for Hulk during its second weekend back in 2003. Perhaps it is possible Man of Steel won't be the huge hit the opening weekend portended.
71% is the Friday-to-Friday drop-off, which is inflated because the opening Friday includes the midnight sneaks. The drop-off for the full weekend looks to be about 65%, which is still hefty, but not as bad as Hulk
It's locked to be a hit relative to its budget and a sequel is assured. Worst case scenario for the domestic gross is $275 million, and Warners will no doubt strive to give it the push it needs to get to $300 million. It's looking good for $400-450 million from international markets, so the worldwide gross should be north of $700 million.