Marvel Comics is back in the teaser business, releasing an image Friday afternoon filenamed "Hero Teaser" along with the copy "A Long Awaited Return..." and the quote "I knew this was my chance to be a hero."
While the immediate implication, based on the symbol, is the return of the original Captain Marvel, Mar-Vell, he's had a few returns in recent memory, though they have always been one-off stories or bait-and-switch type fake-outs.
It could refer to his son and predecessor, Genis-Vell, who served as Captain Marvel for a time, and who also operated alongside the Thunderbolts as "Photon." While Genis-Vell doesn't have quite the following his father once did, he's been absent from Marvel Comics since 2006, having been banished to the Darkforce Dimension by Baron Zemo in Thunderbolts #100.
With Zemo back on the scene as of Standoff, and a new Thunderbolts team spinning out of the series, a return for Genis-Vell may be in the cards. Were either Mar-Vell or Genis-Vell to return, it's unlikely Carol Danvers, the current Captain Marvel, would cede the title to them, leaving the question of where a Vell would fit in the Marvel Universe.
Another possiblity is the return of Richard Rider, the original Nova, who has been missing since 2010, when he was trapped in the "Cancerverse" as part of "Thanos Imperative", and whose helmet bears a similar symbol. In a recent interview with Newsarama, current Nova scribe Sean Ryan hinted that Rider could make a return to the title, though his language was not definitive.
Whoever returns will seem to do so during the Avengers' Standoff crossover event.