>>51087512many anons recommend getting a 390 instead of a 970 since it has more VRAM. If you intend to keep the 970 for a long time before deciding to upgrade then it is not the best option. It is a reasonable option if you want a GPU right now until something decent comes out in 1~2 years time.
you should be fine with a 970 until a proper upgrade is available anyway. If oculus stated they will target a 970 as minimum spec then you would expect it to run all the games initially fine before reaching the slower 0.5 VRAM.
The resolution of the CV1 is 2160x1200 which is not that far from 1080 though you might have to render the same scene twice from a different angle until a more efficient is used, but even then it is not a problem VRAM wise since your card reuses the same textures and assets. If worse comes to worse you can tone down memory hungry settings a bit without impacting visual quality significantly.
If you can manage with a cheap 970 for 1~2 years until GPUs hit another node shrink you'd get more for your money than throwing all your eggs in one basket on a 980Ti.
you could aim for the latest flagship then or a mid range card at 17nm with HBM which could have close performance to the 980Ti or better while using less power. And perhaps include newer features important to VR and perhaps better support for DX12 making it a better option in the long term.
If you have a lot of money to throw away and won't regret your purchase once newer cards are out shortly after then feel free to shell out your shekels for a 980Ti.
Otherwise get a decent bang for buck card for now and wait for the node shrink, because they don't happen every year and that's when you will get the most longevity since GPUs do not generally improve significantly performance wise for the same price range on the same process node.
If pascal is going to be 17nm finfet with HBM then it will definitely be worth the wait, it is scheduled to release somewhere in 2016. Best to wait until then
