I think JB coming into play by one of the big 3 is a possibility due to their NorthEast US route system which is the bread & butter of the US domestic route structure for the network carriers. I think it's a slim chance, but of the remaing players, I think this is the possibility.
I think the current scraps are too small to be worth the effort...especially HA and AS. If DAL, UAL, USAA wanted the west coast/Hawaii market...they would have it. DAL already bought Alaska Airlines...back then it was called Western Airlines. They took all that lift and moved it out East. American already bought Alaska Airlines TWICE, the first time it was called Air Cal, the 2nd time it was called Reno Air. They took all that lift and moved it out East to. If DAL, AA, or UAL were to buy AS, they would do the same. DAL, USAA, UAL all have more 737's then AS has, buying AS would hardly budge the needle for any of them. There are certain expenses that do not scale well when merging airlines and I quite frankly don't believe that AS and HA are big enough to make it worthwhile. HA is 1/4 to 1/3 the size of AS depending on what you are counting, they REALLY don't budge the needle. A combined HA/AS/JB would still be only 1/2 as big as any of the big 3 airlines.
I think what is more likely then any of the above is some consolidation on the 2nd tier. I'm thinking like a HA/JB or AS/JB or AS/HA type scenario is the most likely next domino to fall. Once we get some consolidation on the 2nd tier, only then does that combined airline become a target for one of the big 3.
A JB/AS/HA merger would create a pretty nice looking route map, and with all 3 making money, you gotta think the combined group would continue to do so. Take all the HA W/B's operating on the West Coast, replace them with Alaska NG's and new HA NEO's, and put the WB's on the East Coast flying to deep Europe with some MAX's and/or NEO's flying to "Near Europe" and the route map for the new Blue Hawaii Alaska Air is starting to look a little impressive.