Spoilers ahead for Uncanny Avengers #2.
Uncanny Avengers has always had a unique line-up, being a mixture of X-Men and Avengers in what Steve Rogers calls his "Unity Squad." But this week's Uncanny Avengers #2 revealed the return of a second-generation superhero whom Marvel has been careful not to name in advance solicits.
In the final pages of Uncanny Avengers #2, Cable and a new A.I. in his armor called Belle are in the year 2087. They're at Boston, which has been ravaged by a plant-like virus that first came to bloom in Uncanny Avengers #1. In this future, Belle says Boston was "the first city to be quarantined.. and the first to be destroyed."
The Uncanny Avengers #3 solicit does have text that now seems to allude to Cable joining the team, saying "Plus -- the surprising final member of this series makes a grand and bloody entrance."
Finding a newspaper from the present time battle in Uncanny Avengers #1 and #2, Cable preps to timeslide to join in the action and prevent what he's found in Boston.
After that final page, Marvel published what looks to be a new cover for Uncanny Avengers #3 with Cable wearing an Avengers pin. This cover hasn't been released before, with the December solicits for that issue showing only Tradd Moore's variant cover.
Uncanny Avengers is scheduled for December 9.