Hawkins' character Heath went missing during the Season 7 episode "Swear" and hasn't been seen since. He might be dead, but as the stars of Fear the Walking Dead will caution you, don't assume anyone is dead until you see the body.
It seems clear that Hawkins' departure from The Walking Dead was so he could go do 24: Legacy (and maybe Six Degrees of Separation on Broadway), and his incomplete ending is to allow him to come back when the time is right.
So is that happening soon? Hawkins' representatives declined to comment, and a representatives for The Walking Dead haven't replied as of press time.
If Hawkins does return, it would probably be in the second half of Season 8 at the earliest. Season 8A is in production now, and Hawkins is starring in Six Degrees of Separation until July 16. If his part was already written, maybe he'll show up in the midseason finale, but if not, a rewrite may have to happen to create room for him in 8B.
As for what he'd do, he'd probably come back as a guest star to say goodbye and impart some crucial bit of info on how to defeat the Saviors he picked up during his time in the wilderness before dying. Maybe he'll bring back yet another new group of people who can help the Alexandrians, or maybe he'll pass along a warning about the Whisperers, an enemy who emerges in the comics after the All Out War storyline the show is currently acting out.
The Walking Dead returns this fall on on AMC.