I can't see this happening.
Frank will most most likely manage Chelsea again one day, but that's when the club is being run properly, and he's increased his reputation (e.g keeping Cov in the top flight / top half team etc), that way he can demand certain criteria such as transfer budget.
I can't see England being a threat either (at this time). Look at Southgate. Did pretty well, but he wouldn't get a Champions League club now as a manager. That's if he's sucessful. If, like most England managers it doesn't work out, he'd be lucky to get a low end Premier League club.
Also...He's not the most loved character in the world, and never has been! Look at the sh*t he's taken this season at Stoke and Southampton. Bringing Cov back to the top flight, and then jumping ship to Chelsea.. The scrutiny he would face...
I think the main dangers would be a Fulham or Crystal Palace. Local to him, and established in the league now. He'd have a bigger budget, and wouldn't face massive expectations in his first season, but I think we're going to surprise a few people next season.