You mean like the amazing benefits we got from SandyBridge 32nm to Skylake 14nm ? Manufacturing process doesn't mean faster performance, more to do with the architecture being used.
Last time I checked, this was the GPU forum (despite Gibbo's Skylake advert

).
And besides, you're wrong about the improvements - you're looking in the wrong place. Yes the CPU side hasn't improved much, but the integrated graphics have. Intel is devoting more and more transistors to its graphics each gen.
Let's forget about CPUs, eh?
Look at this way 28nm cards have gone threw many generations and each generation showed a decent increase in performance.
Yes, and AMD at least have made lots of architecture improvements
as well as the die shrink.
This is just more reason to believe the next gen will be worth waiting for.
I have the same worry as with currently CPU's right now that a new manufacturing process isn't going to show a lot of gains right away until they learn to use it better over the generations as they did with 28nm and create architectures that can benefit from it, I think the days are long gone regarding massive upgrades because of a new manufacturing process.
You're basing this on what?
So I say get the 980Ti and enjoy it, I have one for 3440x1440 too and it is great for that resolution and don't see me updating till either big pascal shows a decent % increase or wait for the next big generation and look again at the increase. The thing with computer hardware is there is always something new around the corner, but it doesn't mean it is a lot better than the previous generation as we have seen with CPUs.
I updated from a 780Ti a more powerful card than a 970 to a 980Ti for this resolution and can max out most of the games apart from the usual suspects that we all know if we had 4 graphics cards wouldn't make a big difference to them.
So get the 980Ti and enjoy it and sell your 970 while it's still worth something and it is a good upgrade that you see in real world use not some lame upgrade that doesn't show any real world gains and only in synthetics.
I'm happy that you enjoy your 980ti. No doubt it's a great card. But it's £500, will be EOL in the not too distant future, and really not a good purchase for someone who wants the best bang/buck and doesn't mind waiting a little.
The only exceptions are if either money is no object, or waiting 4-6 months is out of the question. If you're going to keep your card a couple years (perhaps that's not the "norm" here), then waiting a couple months is a good idea.
If you have the cash to change your card every year, then there's no point in waiting. But in that case you'd have a 980ti already. We have to assume that those who don't are not quite as loaded
