LEGO in two press releases announced their cooperation with Marvel and continue their relations with DC Entertainment, owned by Warner Bros.

According to the press release by the multi-year agreement starting as of January 1st, 2012, Marvel has granted LEGO Group the rights to develop a distinct Marvel branded construction toy collection -- LEGO SUPER HEROES -- which will bring the characters, vehicles and action of Marvel's renowned universe to the world of LEGO.
First sets are scheduled to launch in May of 2012.

Classic Marvel comics series such as - Avengers, X-Men, Spider Manwill take place in the new Lego Super Heroes.
Avengers will add to LEGO Minifigure collection such characters as Iron Man, Hulk, Captain America, Thor, Hawkeye, Loki and Black Widow.



The LEGO X-Men collection includes minifigure comic versions of Wolverine, Magneto, Nick Fury and Deadpool, while the LEGO Spider-Man sets offer minifigure comic versions of Spider-Man, and Doctor Octopus.
The first buildable characters in the LEGO SUPER HEROES collection are highlighted by Captain America, The Hulk and Iron Man.

Some heroes will be release in Action-Figures format(prototypes looks similar to Ben 10 sets):



Minifigures and Action-Figures were presented by LEGO at the San Diego's Comic-Con Intl..







Before that agreement Marvel based sets were released by Mega Bloks. Now LEGO will compete with them. So at the beginning of 2012 we will see old Mega Bloks and new LEGO sets taking place in Marvel Universe

According to official thread at Bloks Forum. Mega Bloks will release classic Marvel sets till the end of 2011 (that matches the information that LEGO will release sets at the beginning of the 2012) and in 2012 Mega Bloks will release sets based on upcoming "The Amazing Spider-Man" movie. So the LEGO will release Spider Man sets based on the comic book series instead of upcoming movie.