On what legal grounds do you think this hold merit? I know people don't like it, but there is nothing "wrong" or "out of contract" being done by SF by implementing this plan.
Their contract to you as a season pass holder is free and unlimited visits (within posted operating hours) to the park.
As I see it, that has not changed. Therefore any class action suit on that behalf has no legal merit.
Now, if SFGAm (or SFoG and SFMM) season pass holders who bought their passes based on DejaVu opening "late spring" were to open a case, then they would have some (not much, but some) legal standing as the promotional materials sent with the pre-season order form claimed that they would be working by now.
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"It's Deja Vu all over again." - Yogi Berra