Kane agrees to a multi year extension prior to trade.
Obviously Van is missing the playoffs, but if Kane signs an extension they can justify trading for him. A trade would (hopefully) keep a contract extension lower in cap hit and contract term length than UFA bidding wars would result in. Maybe 3 years at 7M?
Van gets a 4th rounder to keep their scouts on their toes for draft day.

Buffalo gains and NHL regular in Granlund. A defense (PPK) specialist with offense potential (19 goals last year in 69 games). He's only 24 but due for a slight raise in salary.
They also receive a former 1st round pick prospect in Goldobin. Over a Point per game in the AHL this year, just cant seem to click in Vancouver. A move to the east could do the young Russian some good.
The 2nd round pick is very likely a top 40 pick.

Not much to say, who wouldn't want Barzal at this point.
Ideally the playmaking center for Boeser.
Van needs a pick back to restock what they're giving up in this deal.

Demko has a ton of potential. Should be a #1 goalie. Just recently put up a shutout in the AHL All Star tournament's championship game.
Gadjovich is another young prospect with a lot of potential. Could be a top 6 NHL forward, too early to tell. Won gold at World Juniors.
1st round pick is very likely a top 5 to 10 pick. Unprotected, could end up being 1st overall.

Likely a late pick, 50 - 62 overall?

Good playoff depth. Vanek still has skills, 2nd on the team in scoring for Vancouver. Good size and has been healthy this year (so far).