That would be odd. They have Marner, Nylander, Moore and Kapanen at RW. Who goes to the 4th line and who goes to the press box? Nevermind that the Leafs have zero cap space and the problem in Carolina appears to be money.
In theory, Nylander can move to the left and Williams on the right.
Hyman - Matthews - Marner
Nylander - Tavares - Williams
Johnsson - Kerfoot - Kapanen
Engvall - Speeza/Gauthier - Timashov/Moore.
One of Gauthier or Timashov would need to be waived. Of course remains the possibility someone like Johnsson is traded.
Cap wise, the going theory seems to be Ceci getting tossed somewhere. Since moving to the bottom pairing, he's been acceptable. I'm sure some bottom feeder would be willing to give him a shot, see if he fits, and maybe work out an extension. (And again, still lies the possibility of someone like Johnsson being moved).
All that said, that's just in theory.
I think everyone's bets would be on him returning to Carolina. I don't think anyone is actually expecting Williams to be a Leaf, but it's interesting they've reportedly "pitched" to him.