This is good news. Academic publishers are parasites and anything that reduces their stranglehold on academic knowledge is good. That said, parasites are, if nothing else, resilient.
So, there's a few issues that I'm concerned about. First, it's not clear to me that university libraries will be able to drop their subscriptions to these journals based on this decision. The vast majority of research receives some federal funding, but there will still be some subset of articles that are funded through private research grants and will still sit behind a paywall. Journal subscriptions are a huge drag on library budgets, so freeing that money up would be immensely beneficial. Second, I can see the journals reacting to this by going full open access, but charging massive "fees" to publish. Right now Nature charges >$10k to publish open access, and I'd expect them to ratchet that up as it becomes their primary vector to siphon tax payer money into their own pockets. This seems to be the playbook based on the European "Plan S" push for open access.