Sure. Those ads happened twice. Both can be called false advertisement by now I suppose. Given recent update from CDPR that some got:
For now we don't have such plans. Should we decide to release The Witcher 3 to other OSes than Windows, we will let everybody know.
Another one was only very slightly more optimistic:
Many thanks for reaching out to us again. We are still looking in to Linux but there is nothing concrete I can offer – we cannot promise we will release W3 on linux.
If the situation will be more clear we will make a public announcement.
Business Development Manager