Given the history of the Titan cards from Nvidia its reasonable to expect a new model to made from the latest ASIC. Most likely the Titan will be between the Quadro and RTX 2080 Ti cards available now.
Given the Quadro card, its likely the RTX Titan will ship with 12GB of VRAM.
It could be that Nvidia is awaiting the new node to become available at TSMC. At that NVIDIA may deliver a new series of cards with some redesign of the current Turing core layout.
We speculate that if Nvidia was to split up the Cuda cores from the AI logic and the Ray Tracing into separate chips would allow for more sophisticated design down the road. The power would be far easier to manage.
RTX 2080 Ti cards need dual 8-pin power connectors which necessitates 850W PSU as a safe minimum. 1000W is probably best for dual card rigs. RTX Titan cards are likely to be just as power hungry.