No, they can pay him whatever they want to pay him.
If Nance is at the end of his contract, neither Fox or NBC will be beating down his door to offer him a big raise.
Saying Romo can't make more than Nance is like saying Amari Cooper can't make more than Beasley...
Tony is gonna get paid and it surely means more money for Nance too.
"Romo’s contract is up after next season, which could set up a multimillion-dollar TV free-agent sweepstakes for his services at this time next year.
Before that can happen, CBS is prepared to give Romo a substantial raise from, according to sources, the $4 million range that he currently makes. Next year is the final season of his three-year contract. It is hard to see how he does not become the highest-paid NFL TV analyst.
If Romo does make it to free agency, CBS would have the right to match an offer. CBS has a history of negotiating contract renewals early and, with someone like Romo, the network is trying to implement this strategy again, according to sources."
https://nypost.com/2019/01/21/cbs-is-trying-to-end-any-pricey-tony-romo-tv-sweepstakes/