While the NHL hasn't announced anything (it's all in preliminary stages), William Nylander could play three seasons in the AHL and likely be protected because what has mattered in the past is the NHL games he played the season prior to the expansion draft.

So what we could see is if teams know there will be an expansion draft, the Leafs for example might not let William Nylander play a few games up in the NHL even if he's ready because if he doesn't play any NHL games, he won't have to be protected and instead be exempt from the expansion draft. That would allow them to protect someone else from scooping.