At least in Iron Man it was a 3 second cameo where we only saw his back, and then he turned around and we saw his face for a split second, and then he was gone.
Technically, Marvel have no plans to release their own films. They produce their own films then sell the distribution rights - to Paramount in the case of Iron Man.
FunkmasterT is right. Film release, and film distribution are separate tasks. Marvel are releasing their own films (from newly formed Marvel Studios). Whoever distributes them is neither here nor there.