Damn, dat difference between 980TI and Titan X.
There's no reason to buy a Titan X now. Unless you need the extra ram.
I'm willing to bet you can push a Titan X a lot farther than the 980ti. People have already noticed that the 980ti is runs higher than what it says it's clocked at. There's a custom bios out that can push the Titan X to 50% more power.
Probably not enough to make the $350 gap worth it to some folk, but there will be some who'll still pay the premium.