After Sony commented that production on Spider-Man 4 has been delayed, Paramount Studios and Marvel Entertainment immediately moved Thor up two weeks into Spidey’s May 6, 2011 release date (Variety).
With Thor abandoning its original May 20, 2011 release date, Disney was swift to announce via Facebook that Pirates of the Caribbean: On Stranger Tides (aka Pirates of the Caribbean 4) will be released in Thor’s old slot. Pirates 4 previously did not have a release date. Phew.
The funny thing about the studios playing musical chairs with their 2011 tentpole films is that Sony has yet to move Spider-Man 4 away from May 6. Paramount and Marvel jumped on the date preemptively to have first dibs if Spidey vacates. If Spidey decides to stick around, chances are Thor will move back to May 20 and Disney will move Pirates 4 somewhere else.