There's been a significant change as to how Steam will require games to advertise expansion packs or DLCs on the platform. The new guidelines clearly spell out what can be classified as new extra content and how publishers and developers should handle this future content to ensure that it actually benefits customers.
«By offering a Season Pass, you are promising future content,» the guidelines say. «In the process of launching a Season Pass, you will be asked to commit to a launch time for each content release in the Season Pass. That launch timing is a commitment to both customers and Steam. If you aren't ready to clearly communicate about the content included in each DLC AND when each DLC will be ready for launch, you shouldn't offer a Season Pass on Steam.»
It also spells out the risks of promising DLCs and the like to players. Devs don't just have to provide a launch time, but they need to work to fulfill that promise and release the game when originally intended. «Selling a Season Pass has risks—since you are promising the release of future content—you have to commit to completing that content on time. If customers don't like the content you're releasing in the Season Pass or the timing of that content release, that will be reflected in sales and reviews.»
While it's not too common, there are a few games out there that have stumbled at the hurdle of DLCs. The first DLC that Cities: Skylines 2 released, the Beach Properties packs managed to really rile up players who thought that $10/ £8.49 for some buildings and new trees was a complete ripoff. Then there's Stellaris, which has $200 worth of DLCs. The sheer amount of content here can be tricky for players to untangle, and it's hard to know what is worth buying and what isn't.
«Because a Season Pass is effectively a DLC pre-purchase, creating a Season Pass on Steam has many considerations and restrictions as outlined in the documentation on pre-purchases. For these reasons, we will not offer a Season Pass except
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