According to Michael Ausiello at TVLine, "I can tell you that he’ll have a major presence in at least two Season 4 episodes, both of which are being unofficially billed as 'standalone Governor' installments. No specific intel on when those episodes will air, but I hear they’ll likely fall in the first chunk of eight (premiering Sunday, Oct. 13)."
This isn't the first time that the drama has broken away from the series' main action to focus on a single or a few characters. Last season, an early episode focused exclusively on Andrea and Michonne. Another, later episode took Rick, Carl and Michonne far away from the series' central action for an hour.
"I think that when you see what we do with [The Governor] in season four, you’ll be like, 'Oh, yeah, that is a great reason to keep that guy around,'" series creator Robert Kirkman told us last weekend. "It’s going to be some really cool stuff."
Morrissey's character was widely expected to be killed at the end of last season--but he not only managed to survive, but was brought on as a series regular for season four.