PhoneKing With deference to GOS and understanding how it must feel to have the start up AOSP stepped on by the elephant that is google / android / wait for the courts to break up the monopoly and watch this space, there has not been a clear instruction or communication from the GOS comms team about what users should do in regards to device upgrades.
With deference to all of the people who naturally would like to know what the future holds, e.g., for the Pixel 10 series, Pixel 11 series, etc., I don't think anybody except hypothetical time travelers can be in a position to provide "clear instructions" about device upgrades.
After Google releases the Pixel 10 it will be possible to assess the software artifacts they release with it. If the GrapheneOS team is able to establish a relationship with a hardware OEM, the team will be in a position to provide an outlook after that point.
Meanwhile, I think the GrapheneOS team has been reasonably clear about what they know so far, i.e., the Pixel 10 situation is not known at present, and the GrapheneOS team is in discussions with at least one OEM.
Heck, not even Google is in a position to provide "clear instructions" about device upgrades. If, hypothetically, they must, or they choose to, sell the AOSP effort and/or the Pixel business, it will be somebody else making decisions about whether/when a Pixel 10 ships, with what software, with which licenses.