Minor spoilers ahead for Guardians of the Galaxy.
Not that anyone seriously doubted it, but yes, that is Adam Warlock's cocoon that appeared in Thor: The Dark World and Guardians of the Galaxy, as part of The Collector's larger-than-life museum of Marvel Universe curiosities.
"There are the slither creature from my movie Slither behind The Collector, those guys are pretty obvious. You have Adam Warlock's cocoon, you have all sorts of other characters from Marvel movies."
And since we've heard from more than one person that they're pretty sure the cocoon was open and empty after the Infinity Gem laid the Collector's lair to waste...
For those wondering what's going on, Adam Warlock is a Messianic figure engineered as the perfect human...but ultimately he's quite divorced from humanity and his best-known role is in the Infinity Gauntlet, Infinity War and other Thanos- and Infinity Gauntlet-centric stories. He was a member of the Infinity Watch, a group of beings between whom the Infinity Gems were split up after they were taken from Thanos at the end of The Infinity Gauntlet, and the character at the center of a recent, short-lived feud between writer/artist Jim Starlin and Marvel Comics.
That conflict, which inexplicably took the character "off the table" for a time, led many fans to assume that he would be appearing in a movie soon. The most likely candidate now seems to be the 2017 Guardians of the Galaxy sequel.