The use of "when" at the end of a sentence in this context is simply asking when something will happen, with the connotation that they want that something to happen.

>"This game is broken. Patch when?"

>"I don't like my elected politician. Election when?"

>"Spiders are flooding the Earth. Apocalypse when?"

It is absolutely intentionally incorrect grammar usage.

**Edit:** This usage is not typical in written or spoken English. Rather, based on my experience at least, this colloquial usage appears specifically within online communities by younger generations.

I believe this usage to be the correct one given the context of the original question referencing the ASCII game Dwarf Fortress, which has cult-classic popularity online.

See these links as examples:
<br>[Half-Life 3](https://www.reddit.com/r/agedlikemilk/comments/bctuog/hl3_when/)
<br>[Black Desert Online](https://community.blackdesertonline.com/index.php?threads/sorc-nerf-when.428677/)
<br>[HOI4 Mod Kaiserreich](https://www.reddit.com/r/Kaiserreich/comments/b5rj1c/nepal_nerf_when/)
<br>[Apex Legends](https://answers.ea.com/t5/Legends-Feedback/Wraith-nerf-when/td-p/7489901)
<br>[Battlefield V](https://forums.battlefield.com/en-us/discussion/165520/support-class-nerf-when)