I do work in a bike store, while 650B tires are currently 'fringe', 29 er & 26" tires are basically splitting our tire selection. While I don't support the 'decline' theory of 26inch, they sell less because of other size options. We will only carry so many tires, that leads to less choices of any one size (26, 29, 750b). Technically selling 'less' could be considered a decline, but a consider a decline as leading to obsolescence, in this case, it more size options.