Avengers fans, you better watch this while it lasts! It might get taken down sooner or later. Several other outlets have had this footage blocked, but this one is still up. It's just the teaser footage, not the actual announcement.
If you want to watch the whole video (which includes Joss Whedon's Comic-Con announcement) for yourself on your iPhone or iPad, download the JARVIS app from the App Store, launch it and say “JARVIS, Rough House,” then go to the “Suits” section, and press the “Classified” folder. That will unlock the entire video.