Here's one of those rumors that's been in the water for a while now, but there wasn't anything really much to back it up. Now, we seem to have got some kind of weird hint from a source that may or may not be a Marvel insider but is probably just some kid messing around with his parents' Twitter account. In any case, it's out there now and worth mentioning:
Internet rumor has it that the Masters of Evil will appear in Avengers 2. This rumor seems to be strengthened by the fact that it ties into other unsubstantiated-but-persistent rumors that Baron Zemo will appear in Captain America: The Winter Soldier. Zemo, after all, has been involved with many of the iterations of the team over the years. Radioactive Man, whose civilian identity will appear in Iron Man 3, was also a member at times.
Coming from the same Twitter account that started all the "Doctor Strange in Thor: The Dark World" rumors came a cryptic tweet the other day, telling followers: "The numbers will lead you....9876541."
Those numbers didn't mean anything to anyone right away, but rather than ignore it, someone brought it to the Marvel Cinematic Universe subreddit, where fans pored over the information and tried to make some sense of it.
One of the redditors, following the clue master on Twitter, then told the rest of the group what he saw (edited here for apparent relevance):