The Quake Champions beta is currently running through the Behtesda.net launcher exclusively, but the complete game will be available entirely through Steam once it launches. A Bethesda account will still be necessary.
id Software seems to have realised that adding champions to the latest iteration of Quake for cross promotion purposes is screwing with their game balance, as Telxvi recently prophesied. So, in true MOBA fashion BJ Blazkowicz is getting a well deserved nerf. This and some other changes have been addressed in a recent developer Q&A.
"B.J. Blazkowicz brings a very aggressive push forward type of combat to the game, but even we agree that his first appearance was too strong. Just yesterday B.J. received his first balancing pass where we lowered the rate of fire, and hence damage output, for the high-rate-of-fire weapons, such as the lightning gun. We will continue to play, watch, and monitor matches and balance him as needed", was explained in the Q&A post.
If you continue reading after that point, it is quite clear that there are more non-Quake characters heading towards the arena-FPS/MOBA hybrid id Software and Bethesda are cooking up.
The other big news regarding Quake Champions is that the game will be unmoored from the Bethesda.net launcher, following a full release, and become available directly through Steam.
"Quake Champions will indeed be released on Steam. You will still be required to have a linked Bethesda.net account, but users playing the game from Steam will not go through the Bethesda.net launcher. During the current beta period the game will only be available through the Bethesda.net launcher."
There is still no official release date set, but Telxvi reckons that the game will launch once the number of pay-to-unlock guest appearances reaches a critical mass sufficient to make Quake Champions commercially viable.