If you can afford the Titan then go with that.
Edit. I will actually explain that before I get jumped on.
Last year I had a real result financially and ended up with a big windfall. It left me with around £3500 to build a PC.
Up until then I had a FX 8320 and a 7990, I was more than happy with both. However, having Titan money and indeed buying two for £1300 taught me one thing. It basically allowed me to skip a good few cards after, and, tbh? even with the new Titan X I won't be replacing my Blacks any time soon given that the X performs worse than SLI Titan Black.
So I got to sit back and skip the 970 and 980 and the Titan X. Had I bought, for example, a 3gb card like the 780 or 780ti for up to £500 each I would now be looking at replacing them, given the 3gb is starting to creak and is downright insufficient for 4k.
A guy I know quite well bought two Titans at launch. Here he is two years later replacing them. Two years is a long time in GPU upgrade time. A very, very long time.
So the Titan X will last you for ages, providing you're not at 4k yet. Is it too expensive? well yeah, you bet your ass it is but it's the only GPU brand you can rely on to last you now.
The only thing that would put me off buying a Titan X right now is the looming 390x. However, from what I do know about the 390x? it has a liquid cooler which whilst utterly awesome is not a practical design. No doubt like most Radeons it will contain a lot of raw power but I'm still not sold on the drivers AMD release.
My next logical upgrade is a pair of Titan X, something no longer within my reach.
However, because I bought Titan Blacks I'm not sweating. In fact, I'm not even phased. It will take the next Titan to get me wanting to replace mine and by then I feel I would have had my moneys worth out of them.
You should have waited. Now you've gone 980 to Titan X, which is kinda silly.
In a perfect world I would advise people to avoid all the mid ranged shit that you end up buying and replacing quickly and use your brain matter and save for the high end stuff. It always lasts far longer.