You are confusing the 780Ti with the regular GTX 780.
The GTX 780 and the Titan are roughly on par with each other - especially the factory overclocked 780's.
The 780 Ti is faster than a Titan in every way except compute performance, where it is artificially restricted.
It has more CUDA cores, is clocked higher, and uses faster RAM than the Titan.
Nvidia will be releasing the Titan Black Edition in February to replace the Titan, which will essentially be a 780 Ti with 6GB RAM and unlocked compute performance.
Virtually nothing gaming related will come close to using the 3GB RAM on a 780 Ti though, so the Titan having double the RAM doesn't matter there.
There will also be a GTX 790 released around March, which will be two 780's on a single card.
This is why I suggest anyone buying a system for gaming goes with Nvidia - they're far more focused on gaming performance/features than AMD are.
You right, just re-read some reviews, the 780Ti does in fact beat the Titan. Though the difference is not worth an upgrade.
The GTX790 will be nice upgrade to the 690, for people who want just one card in thier systems.