I can't see it. Even Nvidias own slides had it sitting at around 25% faster in general gaming performance and we have apparently seen the 3d mark scores.
Yes, I expect ~25% faster stock vs stock but my numbers are based on 1080 hitting ~2.5GHz max OC. I have since realised that a 1080 hitting ~2.5Ghz from ~1800 boost would be a similar max OC compared to 980Ti getting ~1.6GHz from ~1150 (give or take a few %). So a max OC 980Ti should theoretically maintain it's performance ratio compared to mac OX 1080.
It's the old mistake of comparing max OC vs stock and selectively forget that the older card also overclocks.