WS will do what they will do; as pointed out that's all for another thread and until it's actually released and in use by paying pax there's no way to realistically compare it to AC.
AC will do one of four things to respond, in order of likelihood.
1) Nothing (most likely). Unless their J loads drop significantly, they won't care. Same as with other routes where they have competition.
2) Work on improving their service and driving this as the marketing point to ensure they don't suffer a reduction in J loads.
3) Lower prices to be competitive. See point 1.
4) While unlikely - they will start to take things away from J (like inflated seats) to save costs maybe in concert albeit unlikely with better pricing.
There could be others.
And without getting too offtrack here, AC also has the advantage of a somewhat decent FFP that is seen by many as superior to what WS offers. If I was a AC SEMM with no copay on TATL routes and was flying on Lat FPs ... I doubt I'd move to WS. I'm sure AC knows (well maybe, it requires someone to pull data) how much of their J load is from loyal customers in these sort of situations.