You can see the image above and below, what he had to say about it:
Got a little somethin for ya, folks. Just cuz you’re awesome, check out this new Iron Man poster for Avengers #AgeOfUltron.
And don’t tell 'em I told you, but there’s a big announcement coming in 8 days… Shhhhhhh… #getexcited
What will the announcement be? the first thought for a lot of fans might be an Iron Man 4. It would certainly be something to get fans excited -- and an unexpected wrinkle in the current slate -- but it seems more likely to be related to the recent Spider-Man deal, or perhaps even just the first full look at Age of Ultron's take on The Vision.