Paraphrasing here, he says:
"My gut says Pettersson is gonna wanna move one...my gut and a little bit of knowledge...Wild fans know that if I say something I usually got a, you know, I don't just throw stuff out there". And he doesn't just throw this type of stuff out there. Anyone who has listened to him or followed his journalism for any remotely significant amount of time knows that about him.
He knows something from a source that he is confident in saying through an official medium that Pettersson is going to want out. When he says "going to want out", it's not to say "he doesn't now, but by the time his contract is over, I think he will". It's saying, "when his contract is over, he's gonna leave" with the implied undertone being "he would leave now if he had any control over it."
It's a rumor because he's reporting that Pettersson doesn't want to be there any longer than he has to. It's not speculation because he has inside knowledge on the topic. Speculation would be if we all sat around yesterday saying "I don't think Pettersson is gonna wanna keep playing there because X, Y, Z." Russo has inside knowledge to the point where he's confident enough to bring it up on The Athletic podcast. I get not everyone listens to Russo on a regular basis, but that's why he even confirmed in the podcast with "Wild fans know I don't just throw this stuff out there."
But HFBoards mod powers apparently also come with a third eye and greater wisdom of the natural world that make them the subject-matter expert on things like this so oh well, what can we mere mortals do. That is to say, you can change the prefix to whatever you want, but it doesn't mean it's not a rumor.