I think the right way isn't "learn a HDL", it's "learn digital electronics design". Hardware description languages enable succint hardware description, but it's still necessary to keep an image of the actual hardware in mind.
You're going to need to commit a lot more time than that. HDLs and the surrounding concepts have key fundamental differences from software that a lot of developers have a hard time stomaching. That's why high-level synthesis is the FPGA industry's City of El Dorado; software developers would be able to create acceleration designs without having to build up a fairly large new skillset.
I've never understood this argument. The change in mindset is extremely small. It's merely a matter of awareness. High level synthesis can work just fine if you don't go overboard with constructs that are hard to synthesize. There is no fundamental reason why a math equation in C should be harder to synthesize than the Verilog or VHDL equivalent.
I think HLS is oversold. It's not that hard for software guys to learn some digital logic and write an accelerator. One or two weeks and it shouldn't be a problem. Where the real problems lies is in the tooling. You can't learn that in one or two weeks. You first need to damage your brain to be able to handle it.
I'm assuming that if public knowledge of AMD's efforts are at the patent level, it will be a few years before there's much to work with, by which point you'd have a solid foundation from which to accelerate your learning.
While sibling comments mention that it is probably wiser to learn digital logic before HDL (and I agree with them), I think it is important to also consider that there is now High Level Syntehesis where programming languages similar to C (e.g., OpenCL) can compile to VHDL. HLS may lower the barrier for programmers to take advantage of FPGAs. However, whether the design can compile to fit the constraints of the FPGA available is another question that I do not know the answer.