I was joking the last time I was at the mile range with a guy shooting a 300 PRC. My range gun is a 300WM 30" barrel with AICS mags. I load 77gr of RL-25 under 208gr Amax/ELDM. 3050fps with COAL of 3.6". I said I had a DIY 300 PRC.
My answer to the question is I think the 300 PRC will fade as fad. The 6.5 PRC might last a little longer. I am using the WSM lineup as a basis. This is just my prediction. I could be wrong, because if I am never wrong I should be a millionaire with my fortune telling!