Here is the bottom line. McDavid isn't moving from Edmonton, unless he demands to be traded. After July 1st, he has a full NMC, so he dictates where he's going.
I don't believe that he's going to demand a trade, but what do I know?
If he asks out, he has the rights, to dictate where he is going.
If somehow he went to Oilers management, and said, please trade me to Toronto, I want to play with Matthews... then they are pretty much either going to do that, or have a completely disgruntled player.
So, if Oilers brass phones Dubas, and says, McDavid wants to be traded to Toronto, what are you sending back...that's pretty much the way it's going to go. Whether it's what Edmonton wants, or if it's best for them... it's pretty much going to be Marner and a collection of lesser pieces/prospects/picks. (Mitch has no NMC until 2023) (Despite what others might think, we aren't moving Matty or Tavares)
No team, who has a star player dictate they want out, with a full NMC and control of their destiny, ever got maximum value.
First, it's doubtful McDavid would ask out, (though I wouldn't blame him at this point), second if he does, he controls where he goes, and the return won't be optimal to the Oilers.