Just keep in mind that every highly successful MMA practioner today has been forced to be well-rounded. This is not the late 80's/ early 90's any more. Back then there was a movement to see which discipline was most valuable and successful. What competetive MMA has shown us is that one must be capable and versed in many disciplines to be sucessful in MMA. That's why it's called Mixed Martial Arts.
Having said that, I also do think that a solid wrestling base prepares an MMA fighter with fundamentals of body control, leverage, and timing timing that can be applied in other disciplines. For example, IMHO GSP's wrestling, while outstanding, is nothing new or noteworthy. what sets him apart is his timing. Again, IMHO....GSP has top-notch, but not phenominal striking...but his timing on his takedowns is what makes him hard ot deal with. Add to that the fact that he focuses on top control as much as possible, even to the extent of giving up a risky, but fight-ending move, and he's turned into a fighter who makes the fight happen on HIS terms. Wrestling can be used to cover holes in other areas as well.
So to answer your original question... I think wrestling is one of three foundational concepts in today's MMA. Wrestling, striking, and cardio/athleticism. You must be average or better in all three in order to compete sucessfully in today's MMA world.
Just my opinion.
"He's just a regular guy, just another guy, we both weigh the same......but he finds a way to win, and I admire it." - Chael Sonnen 07/07/12