You still have 4GB of VRAM, and I'm 100% absolutely certain nobody would have "issues" if it wasn't brought up by somebody running a memory purpose benchmark. At 1440p the 780ti is faster than a 970, so 2 780ti would be faster than 2 970s. I do believe that we had that conversation before. Your opportune upgrade would have been to 980s, or simply stick with 780ti and go SLI.
I'm starting to think 99% of the complainers don't really understand how it works, and why most if not all aren't seeing any real issues with the VRAM setup. The only thing that actually disappointed me in this whole ordeal was the actual spec cover up. I admit they came clean but still. That was total ********. In the end though, the GTX 970 for it's pricepoint is a ****ing BEAST of a card and I don't think anybody getting 100+ FPS in 1080p SLI for 600 bucks should be complaining. On that note, before this happened NONE of the reviewers saw any issues or mentioned of anything weird, and neither did I when testing one myself. Hell, my friend still hasn't picked up his machine and I've been playing with it to purposely find some sort of 'noticeable' flaw without looking at numbers and graphs. If it wasn't for me personally having one here to mess with I wouldn't comment or argue on it so much but since I do I've tried my hardest to get it to show any real problems that others claim.
Poizen @ 4k 980s fall flat on their faces I'm afraid.