I wouldn't be surprised. In the TVLine interview Matt Mitovich asked Katie what Laurel was up to and she said she liked to say that Laurel was on her own island, on her own journey. Matt said "she's a lone wolf," and she said yes.
Then Stephen interrupted and told her that she wasn't, that she had a team member in the premiere. She looks to him and starts to say who it is, but then asks him if it's been revealed and he says no, and she says, "Somebody who we can't mention." That made me think it was a guest star they didn't want to reveal, but it could very well be Oliver. Who knows with her.