Swinney would be crazy to leave Clemson. He is king there and he is the one who created the kingdom, he didn't take over from someone else, it's his.
Unless Swinney absolutely despises recruiting, there is no reason to leave. Otherwise he could end up like Steve Spurrier and Nick Saban as in he'll be out of the league in 3-4 years and will have to go back to the college ranks.
As far as other coaches making the jump to the NFL, IDK... David Shaw maybe?
Maybe Urban Meyer secretly wants to coach in the NFL and his whole retirement from OSU b/c of his health was just a ruse.