Of course Colin is back next season he’s a series regular and one they have wanted from the very beginning, he’s not going anywhere.
Yes- we all knew he was coming back, just not in what capacity (ie they could have knocked him down to guest star, had him feature in the 1st 5-6eps, shacked him up with another guest star- say a mermaid 😉 & we don’t see him again for most the season…kind of like Grumpy, Granny or worse- Jeff, August or Graham 🙁 )- this confirms he will at the very least be a regular, if not bumped up to main for all S3 (I doubt he’d quit his band if he was only going to be heavily involved in Once for a few eps).