The actor, who plays Gavin’s dad Mick Shipman, claims it is a case of “when, not if”.
But fans will have to wait as it “won’t be any time soon” due to the work commitments of its stars, including leading duo Mathew Horne and Joanna Page.
Millions tuned in for the show’s Christmas special last year, which ended with Nessa (Ruth Jones) proposing to Smithy (Ruth’s co-writer James Corden).
Larry, 72, said: “I think it would be pretty cruel to leave us on that cliffhanger. After the response it got at Christmas, you can more or less be certain that, sooner or later, there will be more.
“I’m sure the BBC can persuade Ruth and James to write more, so it’s a question of when, not if.”
He told OK! magazine: “The problem is, logistically, it’s a bloody nightmare as so many people involved with it have very active careers.
“It’s virtually impossible for there to be a whole series, but I imagine there will be another special.
“I’ve always thought a logical thing to do would be a Gavin And Stacey movie, but that’s just my idea.”
Larry’s comments come after on-screen wife Pam Shipman (Alison Steadman) also shared her thoughts on the programme returning.
She told Radio Times there’s no way she “wouldn’t” reprise her role on the programme.
Alison explained: “”I don’t take any notice of rumours.
“But there’s no way I wouldn’t do it. I’d run to Cardiff to be involved.”
She also said she felt “very proud” to be a part of the Christmas 2019 special, which was met with rave reviews.