It makes sense for nVidia to focus on GP100 first due to protecting HPC from Intel and Knights Landing. Wouldn't be surprised that it's ready now but they have to wait for HBM2 availability. But I don't think there's any reason why they wouldn't sell a Titan version, although expect the Titan to be $1500.
Yields. Up until now, the biggest thing TSMC has made on 16FF+ is the Apple A9X, which is only 147 mm^2. Do you really think they can get even half-decent yields on a 500+ mm^2 die at this time? Remember that on 28nm, yields weren't even good enough for a public release of Tesla cards until
November 2012, eight months after GK104 and nearly a year after AMD launched their first 28nm product. Before that, the tiny allocation of working GK110 chips all went to Oak Ridge. And yields didn't get good enough for a Titan gaming card until February 2013.
We could potentially see a really unusual situation this year if Nvidia focuses on the high end while AMD concentrates on a small-die strategy. Imagine if Nvidia releases a Tesla-only GP100 (~500 mm^2) and a consumer-focused GP104 (~350 mm^2), the latter of which would have about twice the raw power of GM204 and beat GTX 980 Ti by 25-35% in most real-world gaming applications. Meanwhile, AMD releases Polaris 10 at ~125 mm^2 and Polaris 11 at about double that, with Polaris 10 falling between Pitcairn and Tonga in performance and Polaris 11 roughly matching Hawaii. We could conceivably have a situation where each company has one end of the market sewn up for a while, with no real competition from the other.