Chiphell shows that the GTX 780 Ti will be based on the same PCB as the GTX 780 and GTX Titan.
It looks like the card has a GK110 chip with 2880 CUDA-cores. The graphics card has a 384-bits memory interface and 3GB of GDDR5. Clock frequencies of 876MHz which can be boosted to 928 MHz for the core and 7GHz for the memory are specified.
If this is correct, the GeForce GTX 780 Ti is marginally faster than Nvidia's GTX Titan and AMD's R9 290X.
The benchmarks were run on a system featuring an IntelCore i7-4970X processor, clocked at 4.5 GHz and combined with 16 GB of DDR3 memory with a 2933 MHz clock frequency. The motherboard was an ASUS' Rampage IV Black Edition and storage was provided by two Plextor M8P SSDs in RAID-0.
The benchmark scores have the GTX 780 Ti is slightly faster than the GTX Titan and comparable in speed to the dual-GPU GTX 690. If these benchmarks are reliable, the GTX Titan will be taken to Berlin woods and quietly shot in the back of the head.