Highly doubt WestJet would join an alliance anytime soon. They have codeshares with most of the long haul Skyteam airlines with Canadian flights already (DL, KLM/AF, KE). To join the alliance, they'd definitely need to update their FF program to be more competitive and offer similar level of ground service as other alliance members. They seem to be following a model similar to Alaska, with concentration in secondary cities (Calgary vs Seattle/Portland) with a focus on domestic/short haul market.