Yes, the strategy is sound. My initial home test with AHIII implied that need for me. It sounds like the 970 will work for it.
There are two points here - the first being the one you made. The second, though, is that I'm trying to purchase now for a second platform and want to be sure that it'll work in the new game. Based on Qwik's comment, I'd say I'm probably safe.
I won't ask about the final transition from AHII-AHIII again. It was a dumb question to begin, given all the "two weeks" joking going on, and I say that without a hint of derision, having done plenty of development projects myself. AH's best strategy is to under-promise and over-deliver; a thing this relatively quiet purveyor seems to do, IMO.
In the end, and as a guy whose home desktops are Macs, though, I'll say I'm very pleasantly surprised at how much Windows desktop you can get for your money. I'm kind of disappointed that nobody seems to sell kits any more (did that a couple of times about a decade ago), but I'm assuming it's pretty easy to kitbash your typical cyberpower or Ibuypower desktop and swap crap in and out as the want or need presents. You PC geeks are winning me over - since you seem to be able to get some pretty good power at a discount relative to and of the Macs.
Perhaps a wirehead here could give me a clue on a different question I'm having. When we start to look at processor and graphics card interaction, how do you evaluate throughput? For example, if you put some higher-end AMD 8-core FX with a 970 and compare it to, I don't know, an i7 with a Radeon R9, how do you evaluate the expected performance delta up front?