Joss Whedon is currently in the process of preparing to shoot The Avengers 2, which according to Screen Daily will start filming in the UK in early 2014. The film will be shot at Pinewood-Shepperton studios, which is where they just finished shooting Thor: The Dark World, and it's also where Guardians of the Galaxy is currently in production.
There's still hardly any information on what story The Avengers 2 will tell, but we know that the usual suspects will be back, and that a few new characters are also going to join them. Chris Hemsworth, Chris Evans, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, and Samuel L. Jackson will all be back. It still has yet to be determined whether Robert Downey Jr. will return as Iron Man or not.
The Avengers 2 will be released in theaters on May 1st, 2015.