Matt Ryan has had an interesting trajectory in the Arrowverse. He once headlined his own show on NBC, Constantine, but that was canceled after one season. Despite that unfortunate fate, the actor and character gained a cult following and he was brought back for a guest starring arc on Arrow. This then lead to more guest starring appearances on Legends of Tomorrow.
It looks like sticking with the character is bringing Matt Ryan back full circle because he has been officially added as a series regular for season 4 on Legends of Tomorrow. The character will have featured on the season three finale before fully being integrated into the cast.
Ryan’s promotion from a recurring to a series regular is contingent on a Season 4 renewal for Legends. The CW is yet to make renewals for next season but Legends — as well as the rest of the network’s DC series — is fully expected to come back.