Me, and many of the other guys I know that have been Renzo fans for the past decade-plus, feel like Renzo had a difficult time getting motivated for matches for a long time. He's financially set, got a nice family, and several successful academies (those that are directly his as well as his cut of his students' academies). Plus, between ADCC and MMA, he had been competing pretty regularly for a LONG ass time.
In his prior matches with Newton and Penn, I felt like Renzo could've won both if he gas tank was a little deeper (IMHO, he took the first round against Penn), which kinda went to his motivation to train. After submitting Miletich, getting a rematch with Newton, and getting to fight Frank (assuming Frank doesn't pull a "Harry Houdini"), I think we're gonna see a stretch of Renzo being motivated like he was back in 1998-2000 (The period where he won ADCC twice, did pretty well in the Rings tourney, and fought Sakaraba in one of my favorite matches).
I remember Renzo saying he'd like to fight Frank years ago, and I believe getting this match is gonna be a HUGE spark in his motivation. (He actually made the statement at the press announcement two days ago that he would've taken the fight for free. See the article at news.adcombat.com right now.) If Renzo v. Frank actually happens, look for Renzo to show up in better shape and more motivated than he's been in years. I'm flying to Mississippi for this fight.