As far as I can understand, AMD has released the specs for the new GPUs, which is what many Linux / Open Source advocates care about, right? Sure they haven't yet added the support for the new cards on their own, but other people could do it if they are in a hurry, right?
Not for Fury, not yet. The shader instruction set architecture (ISA) is up to date, since the shaders are still GCN 1.2 (also known as 3rd gen GCN, IPv8) so you can write shader code for it. But the code to initialize and manage the card changes from generation to generation, if I recall correctly at launch it didn't work at all. Those parts are typically written by AMD, with the code typically preceding and more or less being the initial documentation. From what I've understood it's because AMD's legal department finds it easier to approve low level code than the high level documentation you'd need to write your own from scratch, since the former is less likely to reveal any trade secrets or plans for the future and the implementation is de facto proof the information is sufficient. So until AMD drops some code to dynamically manage clocks on Fury, there's not documentation either.
Once upon a time AMD had a plan to reach launch parity with Windows, since the work doesn't get any significant less by waiting - in fact it would be easier if they could ask the closed source people towards the end of their implementation while it's still fresh before they start moving on to the next generation of cards, but with AMD's financial troubles that's not going to happen. If the open source driver wasn't important for the embedded/semi-custom market, one of the niches AMD is betting on I don't think any of them would have a job today. In fact, I'm not sure how long anybody at AMD has a job as they now have a stockholder's deficit meaning they owe more than their assets. Technically that's not a problem until they can't pay their bills, but I'm not sure how much longer they can get financing since they're now losing the bank's money.