Steam's new policies require season passes to specify content and release dates, with refunds for cancelled DLC.

You shouldn’t pre-order games, but people do it all the time anyway. Increasingly, people have gotten in the habit of pre-ordering DLC too, paying up front for content that won’t be delivered for months or even years,

Actions include removing the Season Pass from sale on Steam, refunding all customers who purchased the Season Pass for the value of unreleased DLC, or allowing customers the option of refunding the entire Season Pass. For the purposes of refunds, the value of unreleased DLC will be decided in discussion with Valve.