Why? TDK was released in late July in similar conditions and out grossed them all.
SM4 could be compared to The Mummy 3 which came out in August 2008 after 7 years since The Mummy 2.
TDK was a great film and had great marketing while whatever Sony puts out will likely be crap and released in early or mid August if it goes summer 2011. There will be more competition and with each sequel earning less than the previous one, SM4 will be lucky to make $300 million. And summer 2011 is much stronger than summer 2008. By August movie goers will save their money if word of mouth is bad plus catching up on films from the biggest July ever.
May
Thor (Par.) - 5/6
Pirates of the Caribbean: On Stranger Tides (BV) - 5/20
The Hangover 2 (WB) - 5/26
June
Kung Fu Panda: The Kaboom of Doom (P/DW) - 6/3
Green Lantern (WB) - 6/17
Cars 2 (BV) - 6/24
July
Transformers 3 (P/DW) - 7/1
Harry Potter and the Deathly Hallows (Part Two) (WB) - 7/15
The First Avenger: Captain America (Par.) - 7/22
Battleship (Uni.) - 7/29
Smurfs (in 3D) (Sony) - 7/29
August
The Mistaken (SGem) - 8/19