I just wrote a big long post about WA-2, it might answer some of your questions, maybe. I think the primary was probably a factor (the total Democratic vote was still 52%, which is actually pretty close to what I would have expected), but there is of course recent polling, such as the poll thread where I posted this:
But re-districting will significantly alter the district--this is because it is likely we'll get a 10th seat here in Washington, and the 2nd district (along with the rest, really) will have to shrink quite a bit. I don't know exactly what they'll do, but Everett seems like the most likely portion of the district that may be cut out, and if that happens, the district gets significantly more Republican. I suppose it is also possible they would try to cut out suburban/rural portions of Snohomish County instead, or maybe something wacky like trying to cut out Island County, which may essentially break even or even make the district a little more Democratic, but this is all speculation on my part. Everett has been a key city in the district for a long time (basically its entire existence), so there may be historical reasons to try keeping it there.
Okay, I just wrote way more about WA-2 than anybody probably cared to read. Maybe RealisticIdealist will have something to add or correct, as he's a more permanent resident in the district than I am. 
WA has fairly extensive criteria for the redistricting commission to follow according to the SOS webpage.
Based on current estimates and a 10 CD map, it would seem that removing Everett and Mukilteo would be the easiest way for redraw CD-2. That is the most compact plan for the district and respects the road connections to Island County. If Everett were left in and Island were cut out then Monroe and the US 2 corridor would have to go out as well to balance population. That would be less convenient and compact, so there would have to be compelling reasons in the other districts to prefer that plan.
