Any word on 1080 being better then Titan X in 4K

So any word that they 1080 really going to be a lot faster in 4k? Right now I have a titan X with a dell 27in 4k monitor. I can't max games out I have to put it around Medium to High Settings. I love to max games out any word on how much faster the 1080 is then the Titan X. Also I know the 1080 has 8GB I'm not sure if going lower to 8GB from 12GB or... Just sit out the 1080 and with for the new "Titan" card. Thanks!