In the past, at least with some increases, they had basically said 'youre grandfathered in this year, but if you want to maintain it next year you're going to have to up to at least this amount'. With how people get established in the same tailgating spots every year, there should be some sort of option for people to have 'right of first option' to play ball at the new level or get out.
At least that gives some people the option. Losing spots is what it is. I tailgated in S4 for several years, and when they took out the lot in the south endzone for the reiman project it pretty much killed our tailgating group, so i can at least empathize with those who are losing. But its the cost of progress.
I am guessing they would say, well we gave you a heads up with that email they sent late last year regarding the change in donations/parking.