They'll just be decommissioned and burn up in space. nVidia will make space-grade GPUs on a 2-3 year cycle.
You do realize that “space-grade” involves process changes that intrinsically incur orders of magnitude efficiency losses? Larger process sizes, worse performing materials. It’s not just a design thing you can throw money at.
They don't need to be space grade, consumer hardware will do just fine.
For AI a random bit flip doesn't matter much.