My understanding is that they just wouldn't get updates, but existing drivers will keep working, and since they're open source, they should at least remain func

My understanding is that they just wouldn't get updates, but existing drivers will keep working, and since they're open source, they should at least remain functional for some time. But it still is a shame, Vega is not that old, and Polaris was very popular. I feel like they might be intentionally cutting them out to try to cause people who were satisfied with those to upgrade.