Agnostic but going with AMD next time. It's just a matter of timing to wait until they're better price/performance, and nV deserves to lose at least one sale over Kepler tanking and the 970 shenanigans meaning I have no faith in my 970 lasting as long as I bought it for.
Last time I bought an AMD/[ATI?] Radeon card, it was for Mom's Win 98 machine. I stuck with the NVidia side of the duopoly just because I "got used to it."
I was actually going to post another thread touching on the 970 fiasco. I think the misgivings are overblown. I also bought one -- mere days before the "Gurr-reat Revelation."
Let me look into my crystal ball, with a thought about what's "past."
I've got an HDTV and an HD monitor. The TV is perhaps 3-years-old; the monitor -- maybe 4, possibly 5-years-old.
The 1920x1080s still dominate the market at their price-point. If you want a "4K' monitor, you'll pay at least $600 to "the-sky's limit" into the thousands depending on size, whether it's "TV" or a desktop monitor and other factors.
To the statistically-likely consumer, this would obviously be seen as a sort of durable-goods investment decision. Are you going to sell and replace your LCD-LED TV over the incremental PERCEPTUAL difference between HD and 4K? The last I looked, the cable-providers were still broadcasting 60hz, even though newer models (of HD 1920x1080) provide for 120 and 240.
A GTX 970 is fully ample for gaming with a single card for 1920x1080. Plenty as far as I can tell! 2x 970 SLI would likely allow for it at 4K. I'm not really clear as to "shortfalls" with a single card and 4K; I'd heard mention of "stuttering" -- here and there, but even that observation and opinion varies.
Are games going to pre-empt you from an enjoyable experience at 1920x1080? Or with 4 cores instead of 6? Not likely. The game makers will aim for a segmented market that allows for the largest revenues in sales. More is better.
So "future-proof" is indeed "in the eye of the beholder" and the beholder's affinity for established HD resolution as opposed to 4K. Long ago, I'd seen people hold on to a Sony color TV set for 15 years. Maybe that profile has changed, but similar imperatives are effective.