I think Stevens is a terrific college coach, but I have no idea how he'll handle NBA egos. I can think of several excellent college coaches who failed in the NBA but almost none who have been successful.
Successful - Dick Motta (1968), Larry Brown (but he had 4 years in the ABA and 3 in the NBA before his first college gig), and Rick Pitino in New York (2 years before taking the Kentucky job).
Unsuccessful - Rick Pitino in Boston, John Calipari, Mike Montgomery, Leonard Hamilton, Lon Kruger, Kevin O'Neill, and I'm sure several others.
The unsuccessful coaches I listed all came back to college and got good jobs, so no risk; but history doesn't suggest success in the NBA for Stevens. Good for him if he beats the odds.