grafena How long does it generally take for Graphene to support a new Pixel?
I think it has been as little as a day or two for some releases. But there is absolutely no way to be sure in advance! When the 8a shipped, Google did something weird (source), so GrapheneOS 8a users had to use a beta release for around a month. Also, I think this drop has more devices than most, so it might take longer.
And who knows? In theory Google might have decided they won't release certain key components for the 9 series into AOSP. It's up to them!
Overall, it seems pretty plausible that there will be GrapheneOS for the 9-series devices within a week after the developers get devices. But it also might happen that it takes noticeably longer, or maybe even never happens.
"It is difficult to make predictions, especially about the future."