This is one of those rumors that isn't about "if" it is going to happen, it's about "when." The page isn't in English so you'll need a translator. Here's a translated quote to whet your appetite:
These days NordicHardware reached by information from Taiwanese graphics card manufacturer to confirm that the launch of the GTX 1080 Ti is only a month away. Graphics Card Manufacturers should already launched production of its new graphics card which internally demonstrated its new models. An exact launch date is not said to be totally nailed but at this moment it points toward a launch in the last week of March, probably between 20-23 March.