Very possible for Happ.
Granted the Jays win the division, which likely implies the offense continues to produce.
There's 47 games left, even with the 6 man rotation he will start 7 or 8 times.
Winning 4 of those will put him at 20.
Optimistically, he would finish with 22 wins.
He might play 9 or 10 games if they go back to a 5 man rotation