Steam has introduced support for season passes—not for service games, but as bundles of already released and upcoming DLCs for games. This update was highlighted by SteamDB creator Pavel Djundik.
Redfall
According to Steam's documentation, the description of a season pass must include a brief summary and the expected release date of future add-ons. If for some reason, an add-on cannot be released by the scheduled date, developers are allowed to postpone its release once. The delay in releasing an add-on is typically not permitted for more than three months. Steam may approve a longer delay, but on a case-by-case basis.
In the event of a cancellation of an add-on from a season pass, players have the right to request a refund for it. To determine the refund amount, they will need to contact Steam support. Additionally, if desired, players can choose to opt out of the entire season pass in such a situation.
Notably, Valve may independently remove the season pass from sale and initiate the refund process for players if the developer delays the content release by a year.
"If you are not ready to clearly communicate the content included in each DLC and the timeframe when the DLC will be ready for release, you should not offer a season pass in Steam," says the platform's documentation.