If a Coach wants out of their contract. They could get out. I doubt teams would force a coach to stay if they wanted to leave, an agreed buyout would be more likely. Infact is there are so few NHL coaching jobs, it rarely happens.
But that is not the point, what you are claiming here, and it's a big stretch. Is a Coach would find an expansion team more attractive than an established franchise all things equal. I find this thinking far fetched. Most coaches want security, want to win, want good players, and most importantly the most money a team will pay them.
Can you demonstrate any of these things Seattle has offered to suggest your position is remotely correct? Otherwise, you are speculating, and it is just an opinion.