Good thought. There are a few buy-low candidates like this around the league. I've been thinking about trades like this as well.
Here's is what I come back to: with as much parody as the Pelicans and Kings both have, I cannot see us doing anything, especially with Johnson's contract.
It would suck to have waited for several years for a star to finally become available, only to make a short-term move that restricts our ability to go after him. For that reason, I'd rather ride with what we have, endure our weaknesses, continue to develop our youth, and wait some more.