I think it's closer than most people might think. I suspect this is largely because there seems to be a wide gulf between most hardware and software hackers (i.e. they don't talk much and tend to throw things over the wall to each other) and FPGAs require you to have a foot in both disciplines. You're right that the mindset required is a hurdle but once I got over that (I'm primarily a software person and it only took the better part of an afternoon), I've been finding it pretty straightforward. I'm struggling more with dusting off my digital logic design skills... I'll get there, just need to get back in practice.
The current state of the open source tool chain is looking pretty reasonable (covering the development life-cycle with yosys/nextpnr/iverilog/verilator/etc) and a few FPGA families having been reverse engineered (the ones I find the most interesting are also the furthest along: the ice40 and ECP5) so you can buy/build open devices and use them with open tooling today. Granted, the devices to choose from are at the low end of the universe of FPGAs out there (i.e. The one part of his talk that I think is off base is replacing microcontrollers/SoCs with FPGAs in most scenarios. At any given process node, the specialized device (i.e. a processor) should be able to crush the generalized one (i.e. FPGA) every time in terms of cost, raw performance and perf/watt and it would likely take more than the current ~2-3 process node delta to overcome that. I don't look at an FPGA as being an either/or proposition: use a microcontroller/SoC for what they're good at in conjunction with an FPGA for what it's good at where the application warrants it. Sure, if you need a tiny bit of software control throw a soft core in there and save the hassle of adding a micro. But don't try to replace a hard core with a soft one just because you can.[1]
[1] Two cases where exceptions seem to be obvious and make sense:
- New/experimental ISAs like RISC-V where you can't readily/affordably source CPUs in the open source world yet.
- Emulators mainly because the ISA you need is typically at least effectively dead. Any devices still available aren't often good fits for what you're trying to accomplish.