Whats your display setup like, what games are you looking to play and are you a quality freak ? If going over 1440p and surround, then yes I'd recommend the Titan for the room, if you're looking @ running it on a 4k tv & or Monitor setup then also possibly as well, but if its just standard 1080-1200p then stick w/ the 780 for now until Maxwell when the game shift happens.
I own a titan personally and run a surround setup of 3 monitors along a/ a 4th (TV) as an accessory for watching videos, chatting etc while gaming though I'm aiming at buying 1440-1600p monitors to replace my setup. I got my titan shortly after the entrance of the 780 but only because I found it for slightly under 900$ at my local store due to an unused return. Had it been its initial price I would have probably gone with the 780SCX.
My question to you would be how often do you upgrade, if not often then what card do you have currently (if any) if not old I'd presume to wait for Maxwell, if outdated and or none to begin with AND you upgrade often, then go with the recommendations from the others above, and you'll be fine till next generation.
My only backup is that with the memory I have I feel I'll be good for the next few generations once more VRAM is required, especially w/ 4k displays coming down in price, I'd say having a single GPU card for pushing the max in games that don't support SLI yet would be an argument but w/ the everupdating nvidia team constantly providing SLI profiles, it won't be to much of an issue over time.
Either way if you can answer those questions I think you'll have a clear answer.