It’s on! Avengers vs X-Men begins April 2012 #AvX
Marvel’s next big event begins when the Phoenix Force arrives on Earth to find a new host. …And the Avengers and the X-Men will be there, which will lead to an all-out brawl between the super teams.
The bi-monthly series begins April 2012 with 12 issues! It will be available for print and digital users. Check out avx.marvel.com for more information.

SOURCE: Marvel.com: Avengers VS X-Men