Le mans: GTE rotary engines?

According to aco regulations, the maximum capacity of a normally aspirated engine is 5500cc or 5.5L. The capacity of the 4-rotor R26B rotory engine (the engine of the 1991 lemans winning Mazda 787B group C prototype race car) is aprox. 2600cc, and has over 600hp. The question that I ask is: Is there a special capacity limit for rotary engines in endurance racing? If so, what are they? If not, how come Mazda isn't completely dominating endurance racing?