Anyone who thinks that Seattle is going to get another airport is a fool. It's much more likely that they would actually close PAE and other existing airports in the state.
Expanding Paine Field will continue to be a tug-of-war. A minor expansion of commercial service there might eventually happen after years more of struggle, but don't hold your breath expecting any dramatic changes.
The crisis that's been slowly building at SEA will continue unabated. Like every other crisis facing Seattle, it was created by the visionary "leaders" and was obvious to see coming for anyone who bothered to pay attention. The solution for that crisis will be the same solution used for every other crisis they've created: make those people who have to get through it suffer more and more, and impose escalating fees on them to discourage use. Only the most wealthy (or those who can wheedle exemption or subsidies out of our great visionary leaders) will be allowed to use these public amenities that we all have paid for for generations (roads, airports, open space, clean water, the list goes on). Regretfully, restricting use of these public facilities will be a sacrifice we all must make, you know, to save the orcas.