That's a steep price but I'd probably do it. Myers is really good.

I don’t think that will be enough to pry him away. I could be wrong but isn’t he their RD of the future? Obviously Braun and Niskanen are there for a couple years while he develops, but then it’s his time.

The Leafs really don't have much NHL depth at centre.. So for that reason Kerfoot can't be traded. Certainly Engvall or Spezza couldn't be moved up to take big #n 2 minutes if Tavares or Matthews were injured.
I'd rather get Dermot trained in the summer to play RHD an keep Kerfoot than made a trade two for one for Myers.

Ummm, Couturier, Hayes, Laughton, Patrick, Frost, and even Giroux play centre in Philly. (with Bunnamon, Rubtosov and Vorobyev (and trade deadline Thompson) all getting 4th line center this year). Not to mention half a dozen other center prospects in the system or arriving next year.

Philly doesn't need centre depth, especially next season.

Kerfoot is almost a one way player and Dermott has underachieved, which is why they've been chosen for this trade.

Myers as a RH dman, with Braun leaving, is worth more to Philly than that deal, (especially when half of leaf fans see Dermott as a weak link, and they're both similar re-sign salary RFAs). Obviously with Lindblom and Patrick injuries, Philly would need a wing if anything and Kapanen straight up is probably equal value based on need and position.

Also, many Leaf fans have said that Dermott can not play RD, and Philly currently has Provorov, Sanheim, Gostisbehere, Hagg (and injured Morin) at LD, so they would need a RD, not a LD Dermott. Philly overpaid to get RH dmen in Braun (UFA) and Niskanen, so cant see them giving up Myers for a LD and a one-way center they don't need.
But I think your premise of Philly needing center depth in 20-21 is a false premise to start with.

If Kerfoot is almost a 1 way player it would be defensive over offensive but hey, saying anything factual on here isn't important