GTX 780 Ti should be way ahead of R9 290X when it comes to noise, heat, power consumed, OC ability, build quality, and industrial design. And with these specs, the GTX 780 Ti will actually have higher memory bandwidth than R9 290X. Min. Framebuffer size is obviously less, but the mem. bandwidth is the more important metric at 4K resolution (albeit not the only important one)). That said, 4K gaming with higher details would require an investment of many thousands of dollars in monitor and multiple GPU's. And due to large advantages in noise/heat/power consumed relative to 290X, GTX 780 Ti would be a more attractive choice in these systems IMO.
Noise/heat/power, presumably will easily go to the 780 ti. They have a lot of leeway to play with.
The build quality, industrial design, OC ability are all up the air. As people mentioned elsewhere, the reference 780 is nothing special other than the cooler is clearly better. It will be aftermarket vs. aftermarket on build quality, OCability, and industrial design, but the reference board itself will likely not be anything special (presumably like 780/titan).
Will the 780 ti at 7 GHz be nearing the limits? I think the 290x is clocked very low and iirc has memory rated 500MHz higher than it's using. I don't know how much memory OCing affects the 290x though, but it may have more headroom if I were to just guess since the memory is clocked so low.
As for 4k, I doubt the 780 ti will beat the 290x. It might come close enough to trade blows, however even that will be somewhat surprising considering the titans weak performance.
It's going to be an interesting battle for the crown. 1080p will undoubtedly be clear, but going higher might not be. To me it seems unlikely it will be undisputed at higher resolutions, which will make the $700 very questionable/overpriced. I could be wrong though, just a guess.