Ken shamrock is, and has been for a while, delusional. The majority of new MMA fans that have hopped on board over the past couple years don't know much about Shamrock, Gracie, Frye, Jimmerson, Ruas, Abbot,Kimo... the UFC would have to do a ton more advertising to make this fight sellable than it would be worth. Brock vs. Cain 2 would do far better.
Plus, you suck Shammy. You've sucked for a while.
And to those that think Royce deserves a shot on UFC Rio... you are wrong. The sport is not the same it used to be and has passed him by a long time ago. Also, he's a cheater... therefore definitely doesn't deserve a shot.