The actual release date is expected to be about two to three weeks later, around mid-March, but there may not be a lot of custom models available at launch.
NVIDIA's add-in board partners weren't too happy about the company's Founders Editions and it seems we can expect more of the same as most GTX 1080 Ti models that will be available at launch will be Founders Edition models:
We were told there is a slim chance for custom models to be ready on time. It does not mean we won’t see custom models, it means not everyone will have a chance to buy one. GPU market is developing quite rapidly, so those things can change as we get closer to the launch, but of course, we will be monitoring the situation.NVIDIA's partners are watching the situation cautiously as they fear the Founders Edition might become exclusive to NVIDIA, meaning NVIDIA would become the only seller of 1080 Ti cards at launch.
There's also a rumor that the GTX 1080 Ti may not be the only new Ti card as NVIDIA is said to be working on a GeForce GTX 1060 Ti. No further details are known.