This is just my guess of blends that could be endangered.
Fribourg & Treyer Cut Virginia Plug, Special Brown Flake and Vintage Flake
Wessex Brigade Campaign Dark Flake, Wessex Brown Virginia Flake, Wessex Gold Virginia Flake
Solani 633 and 660 Silver Flake
i could name more but that would just be adding more blends going the way of the Dodo.