No, absolutely not. To put things in perspective a 20 million dollar deal would put him about at about the 50th highest paid player in the league. He's a great defensive player at a position (guard/wing) where being great defensively is less value and has real offensive limitations to his game as a PG. Other defense first offensively limited guards are like Dejounte Murray at 14.3 next year, Eric Bledsoe at about 16, Pat Bev at 13.3, Danny Green at 15.3. You can argue he should be a little higher than those guys, but 20 million would be a bad contract for him.
I think only Bledsoe is close to Smart in terms of impact from that group. Murray got paid because he's young and promising more than what he's actually done, and both Beverley and Green are vastly overpaid and vastly inferior to Smart.
Bledsoe is a much better scorer than Smart. That's really undeniable. He's also a considerably better rebounder. However, he's a worse 3 point shooter, worse defender by a sizable margin, worse when it comes to turnovers and on the same level as a playmaker. He's also 5 years older and has more of a significant injury history. So I think of the 4 Bledsoe is the only one of good use when it comes to trying to predict Smart's next contract.
Given Smart will be 27-28 when his expires, I fully expect him to get almost the exact same deal - 4 years, $70m or so increasing every year. So an average salary of $17.5, same as Bledsoe. I think that's fair for both sides, unless Smart develops into an elite 3PT shooter, like I said before in this thread