Has the OEM in question been revealed yet? Likely not one of the major OEMs because they all lock their bootloaders. I'm crossing my fingers it's Fairphone but that's because I love my FP5. The GrapheneOS devs have been pretty harsh towards Fairphone because of their slow updates.
Those are no longer big these days so no. Also, they're not going to restart a whole product category just for grapheneos.
As OnePlus is kinda dead and taken over by oppo, I'm guessing Sony. They have some similar collaboration in the past like with Jolla. My Sony XA2 was one of the few models that could run sailfish.
BlackBerry hasn't been OEM for their last few phones - the KeyOne, 2LE, and 2 were all outsourced to TCL, who is still making handsets. This would also fit with BlackBerry's security image, and even pull in the OnwardMobility vapourware.
I'm every bit as skeptical as you are, and in no universe is BlackBerry the OEM in question, but I would like to live in my delusion until GrapheneOS proves me wrong - I want a keyboard, dammit!
If you've run a open source project almost of any size, it's quite a task having to support it on various devices scenarios.
The GrapheneOS devs are doing the right thing for the longevity of the project. Focus on a small number of phones/hardware. It guarantees its long term success.
Excellent work I think, also the Pixel hardware design offers slightly better security with the baseband.
