Given how standoffish Marner has been with the media and the fan reaction throughout the season, and in Game 7, can you imagine the reception he'd get if he did re-sign here? I can't see his family or agent supporting him on such a decision irrespective of his attachment to the Leafs, his teammates, etc.
It's like a lot of us were saying - everyone has a price. I think his is $14M+. If the Leafs are insane enough to offer that, then he'll probably stay. Otherwise, he's going to a rebuilding/playoff bubble team for $14M+ or to a low tax/tax free contender for $11M-$12M (e.g. Vegas).
My hunch is that Treliving WILL put a feeler out to Marner's camp with something like $12M x 8 full NMC/NTC, which will get promptly rejected. It's one of those offers that everyone knows will be there just to save collective face but has no realistic viability. Everyone will breath a collective sigh of relief, and life will move on.