[Speculation] Who should be the next AS partner?
I think EVA Air should be Alaska next partner. Air Canada (alternatively Westjet) would be another choice.
JetBlue would help with AA nearly dropping out in 2018 but that is not going to happen. Domestically, it's not going to be DL, AA, or UA. WN would also be alien though helpful.
Without AA or DL, it may be necessary to abandon AS in 2018.