According to SuperLucha's, Averno has been signed to WWE from his previous company CMLL. This is the same place that Sin Cara (formerly Místico) wrestled at before his signing to the big dog. While I may not be able to understand the article itself bar a couple of passages, a colleague of mine translated it for me and this is what the summary of it is.
He'll join WWE to rival Sin Cara, whilst being re-packaged as an unmasked heel (much like Dos Caras Jr. was to become Alberto Del Rio). Vince McMahon is known to be unhappy with Cara's matches due to frequent botches, so he's signing on somebody that the masked marvel has squared off with many times before. This is also apparently not a major raid of Mexico's box office, much rather to fulfil a specific need and therefore other stars like Fantasma will not be signed. Rumour states that he'll instantly make it to the main roster, bypassing FCW. This rumour also states that his new name will be Miguel Jaurez.
Note though that NONE of this is set in stone yet and we will have to wait for official confirmation from either party, although CMLL are unlikely to make an announcement as they apparently do not know of the signing thus far.