just buy a 1180 next year (possibly will be branded 2080)
i reckon it will manage ED on VR ultra and allow some shiny super sampling all off 1 card. no need for SLI and chances are if you sell both your 1080s next year it will fund the single card. its what i plan to do. Nvidia works VR SLI sounds nice in practice but if hardly anyone supports it properly what is the point (imo).
Yes, I want these cards to see me through to the TI version of the next gen, probably still at least two years away from that.