People will be able to install GrapheneOS on supported devices themselves but it hasn't been stated that it will be the only option. There will be further announcements about support for it.
You guys are going to reach a much wider audience now. Google doesn't sell Pixels worldwide but Motorola does.
GrapheneOS literally puts Motorola on the map for me.
Motorola Mobility was sold to Google in 2012 for ~$12bn, and then in 2014 to Lenovo for ~$3bn.
https://en.wikipedia.org/wiki/Motorola#Split_of_Motorola
No wonder if I see the "crap" my collegues have to endure with their Samsung phones in comparison to my rather quiet GrapheneOS phone. It has security and cost/time consequences. They could configure their phones better but don't care (due to insecurity what could break & complexity).