Vail will never own Mammoth.
The town would throw the biggest fit the ski industry has ever witnessed. Mammoth is expensive, but I don't think any of us our complaining. I'll gladly pay $600 for my MVP pass in May to save some cash, but that's just it, I'll gladly pay $600 for 1 resort.
Vail is a well run business. They treat their employees well enough. But they are killing the other resorts around. Forcing them to drop prices which changes how long the resorts stay open, forces other prices up... and so forth. Vail makes it's money through properties and ski shops, not through their resorts. There is a reason all the vail resorts close in April. There is also a reason that all the resorts around vail resorts also close in April. Abasin is pretty much the only resort that has been able to resist this since it's only partially owned.
A lot of CO season passes were upwards of $800 before Vail started buying up everything. CO resorts also used to open and close when the snow was gone rather than set opening and closing dates.
A lot of CA resorts are still able to do this, but as Vail buys out more, this will begin to change. Pass prices will drop and the first thing to go will be summer skiing.