I did think I actually saw "pandemic" mentioned in some of the terms and conditions exemptions for at leas one of the pass offerings somewhere.
No doubt they'd have to refund all the passes if they went to the price gouging model. They'd probably offer pass holders either a discount on the high priced limited day tickets or refund the money they paid for the pass.. I think at the least, they'd black out the passes over Christmas Break and President's Day if, in fact, they can only operate at 20%. At 50% who knows. They need the revenues and with ski school, lodge food, rentals all taking even bigger hits, all bets are off on pass holders getting full access every day if there isn't enough capacity left for LOTS of day ticket revenues.
I reread the terms and conditions, which only include an agreement not to sue in the liability waiver. I question if this would be applicable or enforceable in a breach of contract claim. They do have a pass protection program which is quite limited and would appear not to apply to capacity restrictions. it does provide a pro rata refund for complete closure.
With regard to refunds, blackouts, discounts, etc., none of this is in the season pass agreement/contract. A very brief search indicates that force majeure is generally not invokable unless explicitly stated in the contract.
Obviously, I hope no restrictions come about, and think that Sun Valley (with the highest season pass rates in the country and no senior discount) would do the right thing (got a 20% credit for the early end this year), but at the beginning of summer, there is nothing better to do than speculate and think up what ifs.