I could see him here in 2020 because he's under contract.
Beyond that, it's nowhere near that simple.
Nobody gives a sh-t if you're a former MVP. The only thing that matters is how good you are now, and even more importantly how good you're going to be in the upcoming years. Any GM who gives you a contract for how good you used to be is an idiot. Our current GM did that once under the old ownership. Seriously doubt the new owner would be so inclined.
For Newton to get a five year extension would require not just a healthy season but one hell of a season, performance wise. And that'd have to take place with a rebuilding roster around him. Could that happen? Sure, but how likely is it?