Still a long time for someone trapped or being held hostage, to be sure, but not as long as the absences between Morgan’s early series appearances.
There’s still some months before The Walking Dead will get to filming Season 8’s final episodes, so perhaps a deal can be struck that gets him back for one or some of those.
(And at least those were structured so that Morgan’s return made sense.)
If Heath would show up before the War was finished, though, that would make way more sense, seeing as how the timeline wasn’t stretched all that long over the course of Season 7.