Valve has changed the rules for releasing Season Passes and included DLC on Steam.
Here's what we know
The company required game developers with a paid Season Pass to accurately state DLC release dates.
The innovation applies specifically to passes with released and upcoming DLCs, access to which is opened by a one-time purchase, and not to battle passes, which are available in service games.
On a special Steam page, developers must detail the content of the DLC and its release date. If for any reason they fail to deliver on their promises, Valve reserves the right to partially or fully refund users for the purchase of the pass and remove it from sale.
Developers can update the DLC release date on their own, but only once per season pass. The maximum period for deferring an add-on does not exceed three months. If it is necessary to exceed this limit, you should contact Valve.
The new rule does not apply to Season Passes, which are included in the extended editions of the games.
Source: Steam