Without warning,Elite Dangerous has made a surprise appearance in Steam.
When asked, developers Frontier Developments have ruled out giving current Elite Dangerous owners Steam keys, but they do say that and other policies can change. Of course, if you have a non-Steam copy, you can always add it to Steam as a non-Steam game.
The Steam version of Elite Dangerous is the same as that available directly from Frontier Developments, down to system requirements and content. This also means the Steam version is lacking many Steam essentials, mainly Steam achievements and trading cards. The only thing that is different is the choice of client and DRM delivery.
Demand is high on the Steam page as well as the Frontier forums for Steam keys, so the studio may capitulate on this soon enough.
On the side, this listing comes a few days after Frontier launched the beta for a Mac version of the game, so this may be the most likely version the game has made to Steam. Who knows? It might turn up as a launch Steam Machines game as well.