I just spotted a teaser poster of Alvin and the Chipmunks 3:
The third film is titled Alvin and the Chipmunks Chip-Wrecked, here’s the plot:
“On vacation aboard a luxury cruise ship, Alvin, Simon, Theodore and the Chipettes are up to their usual antics, turning the ship into their personal playground, until they become ‘chipwrecked’ on a desert island. As Dave Seville frantically searches for his AWOL charges, the ‘Munks and Chipettes do what they do best – sing, dance and wreak havoc. But they’re in for a surprise when they embark on an island adventure with their new friend – a castaway who’s more than a match for Alvin and the Chipmunks.”
Back in March 2010, Fox announced that Alvin and the Chipmunks 3 would be released on December 16, 2011, but filming started a bit late, in January 2011, so I’m not sure if the date still stands.