The KM2s were released in mid-2008, so going on 7 years now. I am not sure when this size was released though. (Tirerack review dates match this release date; they start in March 2008.)
The original BFG A/T KO was released approximately 15 years ago (although only 10 according to
this, which may be Australia specific, I know I had a set in 2002-3. Tirerack reviews start in March 2002.), either way that puts the KM2s at over 1/2 way to their upgrade time. The BFG T/A KM predecessor to the KM2 was only around for about 5-8 years. My tire history is fuzzy, but I know it wasn't released before 2000.
I think that is the trend and that 16" sizes will begin getting hard to find, especially in less common sizes. The 245, 265, and 285/75 sizes should be around a while, but I wouldn't be surprised to see many sizes relegated to "specialty" status. $$$$ and hard to find.