Without supported Consumer Hardware available on the market in sufficient volume, even less end-users will use an alternative OS, which will affect quality and size of the alternative OS-market and fragment the remaining users even more.
This will put the future of the entire alternative-OS ecosystem firmly back into the hands of Google. If they start further restricting BL-unlock on the Pixel-series to e.g. only Google Developer Account-Holders, the whole ecosystem will finally close down.