Technically, Darkhawk has been on earth since last year. As NOVA wrapped, he and Nova were defending Project PEGASUS from a tentacled demon from the Cancerverse as well as "Dark Quasar" from there. Darkhawk was injured protecting the site and Dr. Necker, and Nova left her to tend to him as he pursued Dark Quasar. Powell hasn't been among the mourners at Nova & Star-Lord's space funeral, so it's something which has been left to limbo.
Jack Flag popped up on panel I think in THANOS IMPERATIVE #1 and then has been forgotten since. Which was a shame, I thought he was an unlikely but amusing member of the GOTG. The fact that it was so random and improbable made it work.
Quasar had his own series from 1989-1994, but...so did EVERYONE back then. Sleepwalker lasted 33 issues, for heaven's sakes (which is amazing when you consider Moon Knight barely lasts that long between relaunches anymore, or even Wolverine titles). Before ANNIHILATION, he hadn't done much besides stand in mass Avengers panels for years. Not that this harms him as a space hero, merely proves that space fixes everything. Even the Hulk got cooler in space. Even some spare X-Men like Havok and Polaris got cooler in space. It's a place where threats are epic, and feats of heroism are usually reacted to in saner ways.
At any rate, I doubt the average citizen at Marvel or half the Avengers as written by Bendis know who Quasar is anymore. That might be funny in a way. Have the Annihilators beam into Midtown and have nobody around them know who they are, but then have Wolverine, an infinitely weaker but over-popular hero, walk around the corner and he gets a crowd. I could imagine the snide comments from Gladiator or Ronan now.
Plus, I do wonder if the walking time paradox Namorita has bothered seeing Namora since she's been hanging out at Project PEGASUS too (with Nova's brother Robbie mostly).
The difficulty with ANNIHILATORS has been similar to some of the hiccups with ANNIHILATION CONQUEST or WAR OF KINGS. The lead characters are not the characters Abnett & Lanning are best writing. And while they can still make a good story of it, it doesn't quite come together like an arc of NOVA or GOTG did. ROCKET & GROOT, on the other hand, has been fun.