So AMD had working DX12 drivers for everything they said they would at launch, so did Intel, Nvidia don't have support for the oldest architecture with incidentally almost no real DX12 support anyway but were happy to shout about support for those cards for a year before Windows 10 launched. So now this old generation of cards with basically nothing new happening with it in years for some reason isn't ready?
It's not like Nvidia lie though. I believe the whole 144hz/woeful power efficiency problem they have was ignored for a year, finally exposed to which they immediately promised a driver fix, which has since been restated (fairly quietly) as probably not being fixable without an architecture change. So how long of Maxwell is uber efficient, pair it with our overpriced 144hz g-sync panels, or the even worse priced overclocked panels which(I'm not sure on this) AFAIK aren't even guaranteed at that higher speed... which completely breaks the power efficiency of the architecture. So use 70-80W less while gaming for a few hours a day but use 100W more for the other multiple hours people leave their computers on a day.
970 3.5/4GB issue, Nvidia lie, a hell of a lot. They said it would have support from launch, it didn't. There isn't an obvious reason why it shouldn't except if they found out they just can't get the cards working with DX12, in which case it's another lie.
If they realised they couldn't support it I'd absolutely expect Nvidia to lie about it for a while and hope everyone forgets and just never deliver the driver.