What would the extension look like?
And, personally, I think we need to focus on getting younger regardless if we make the playoffs, (somehow) win the Stanley cup, or miss the playoffs. Maybe a team who cannot fit a young player on their team with the current cap hit, could make a trade with us. Who would you choose? personally, I'd go with Casey Middelstadt or a player of that caliber & hope he works out.
Keeping draft picks would be a good idea as well

I feel like Hanifin would be looking at a deal between Pelech and Toews. Maybe 8x6-6.5M
Hanifin is only 26, honestly outside of the 4th line the roster isnt that old (and Eberle in this hypothetical) very young defense and most forwards are 30 or younger.

Any Hanifin extension screws their cap for next year

Well, Seattle definitely passes.