I'm of the mindset of
"Fish or Cut Bait", while others might say "Crap or get off the Pot" of should stop wasting time and get on with something..
If you know under no uncertain terms that you're never going to meet Nylander's demands of a contract in the 10's then what is the use in prolonging this out?
The best time to trade him would be in the offseason when teams have cap flexibility and can make moves and overspend the cap assembling teams for next year.. Once the season starts it becomes much more limited options because of the salary cap on both sides of any trade and potentially limted trade partners.
The only other plan would be to use Willy as an own rental for 1 year, and then let him walk away next summer, but that is poor asset management which BT already faced with Johnny Gaudreau in Calgary thinking a deal was to be had, then the player simply left. The closer this comes to UFA status for Willy the more likely he would be willing to test the market first to see his # and then decide to return to Toronto.
It be hard to image Treliving pulling a Stamkos here, and offering Nylander a 8 X $8.8 deal today and riding out the season and then having Willy test free agency and then return home for the same deal he could sign today, only now 7 years in term instead. Stamkos tested the market even his home town Toronto and went back to TB for their hard line offer of 8 X $8.5 mil.