Jarryd Hayne has achieved almost everything in the rugby league: he has played for NSW in State of Origin, and played for Australia, either as a full back, winger or centre. If he now is able to crack a spot in the NFL then he will be unique in the annals of Australian sport for his dual sport achievements. This is much more difficult than switching between rugby league and rugby union. Rugby League and American football are radically different sports, despite requiring some common skill sets. To be able to succeed in both sports requires incredible talent and mental fortitude.
If he does come back to rugby league at some point, then the NRL should grant him a special exemption to earn unlimited commercial sponsorships, because that is what he deserves, and the game will be better off for having him play it.