Will the game be fun? Probably. But I doubt you will see more than 50,000 peak concurrent players, and I doubt QC will be anything but a blip on Quake's timeline.
The ethos of Arena FPS has been abandoned by Bethesda. The community has been begging for Bethesda to remaster Quake Live with a modern UI and modern matchmaking. It took 4+ years to implement a party system, so you could join games with friends. The state they left Quake Live in is such a disappointment, especially considering its potential in eSports. How they came to the conclusion that it was the gameplay or the graphics stopping people from trying Quake Live is beyond me. People want lobbies, ranks, matchmaking options beyond quick play, etc.
The demand for photorealism over high visibility has had an unattended consequence in relying on game engines that are frankly too easy to cheat in competitive multiplayer. Even if QC became popular, it would be plagued by the same fundamental client trust issues that CSGO has. I would be very surprised if this game maintained any sort of following through 2018. QC is a serious misstep, especially when it offers nothing but brooding backdrops to compete with Overwatch, which is already a very good contender in the mass-market Arena FPS world.
/r/Diabotical gives me some hope. Reflex has quickly established itself as the replacement game for CPMA diehards. But real Arena FPS has not figured out a way to break into the mass market, and probably never will.