There are some big * on the open expansion bay system.
The PCB (card) format IS open as of now, though there are still some details missing, I expect the PCB to be fully documented, for other companies to develop boards to put in the existing shell people can buy (and some already have if you didn’t preorder a GPU).
However, the shell/GPU housing is not yet available as a 3D model. It might be at some point, and I’m sure any company dedicated enough would be able to reverse engineer it (especially since it might need customisations for the specific molding process anyway).
So any company planning to make a low- medium effort product will only be able to develop a PCB to put into the shell the user will have to buy separately (or replace the PCB in theirs).
Of course, anyone capable of developing GPUs probably can reverse engineer the shell.
But if their intention is not to develop for the Framework specifically, but just to follow the open standard without too much effort, what they could do is develop their own shell system that just houses PCBs of the same dimension, so you could theoretically take a framework GPU shell (should they ever sell that separately) and put their GPU in it, or in reverse, take a framework GPU PCB (should they ever sell that separately), and put it into that companies custom shell that only fits in their laptop. Who knows.