Vin Diesel has been posting some odd stuff on his Facebook page.  The pictures are down now, but take a look at this screenshot.

There is nothing to confirm at this point.  Avengers 2 is still three years off.  No casting, no characters.  Hell there might not even be a script yet.  But Vin Diesel would be a pretty cool Vision.

He was previously rumored to play Silver Surfer.  As we know that did not happen.