If you have read the press about "Pirates Of The Caribbean: Dead Man's Chest" and the 3rd film "Pirates Of The Caribbean 3" then your surely know that these two sequels to the first film "Pirates of the Caribbean: The Curse of the Black Pearl" are produced back to back, right one after another to save on production costs and keep the cast fresh.
At first this sounds cruel for a film-lover. It reveals the obvious proposition behind a film project these days: making money and storming the box-office charts. Filming back to back, having two films completed and then only show one to an audience in theaters is just to maximize revenues. Maybe there was a story that could have been told in one film, but the producers decided to spread it over two films and thus generating 2 times the revenue.
Now, you might think this is a new development. One of those nasty new things that get invented these days, just like prequels and universal releases.
But, you might be surprised to hear that "Back To The Future Part II" and "Back To The Future Part III" were also filmed in one move. Universal produced the films 1989 and 1990, the audience had to wait 6 months after Part II to see Part III.
A more popular example is the Matrix Trilogy, where "The Matrix Reloaded" and "The Matrix Revolutions" were done back-to-back. Principal photography was between March 2001 and August 2002 in Australia. "Matrix Reloaded" came to the screen on March 2003, "Matrix Revolutions" followed in October 2003.
The most extreme example of letting the audience wait so far can be credited to the Lord Of The Rings Trilogy. While the epos was produced between 1998 and 2001 in New Zealand, the fans had to wait for one year (12 months!) between cinematic releases (which were in 2001, 2002 and 2003). Surely to maximize the hype among the fans.
Now, back to the Pirates: While filming is still ongoing as of today, we won't stick the "black mark" on this one too soon. But be sure the studios will film back-to-back again...