Atlanta needs to switch it up... they've hit the ceiling with their current roster and it's only going to get tougher as Johnson's contract escalates.
If the Kings offered up Evans/#5 for Smith(with Atl. possibly kicking in #23), I think the Hawks take it. They save money, get a young G who could be an impact player if he learns to better integrate his strengths into the team game.
The Kings get an athletic shot-blocker to pair with Cousins. They can go BAP at 23, maybe a SF to allow Smith to play stretch-4 or maybe a guy like Royce White to add some ball-handling/passing.