There are a few things to keep in mind that I don't think have been addressed.
First, if a player wants/needs to develop, he will do so best in the NBA (NOT college). This is both intuitive and has been shown through studies. The NCAA and NBA games are very different, and if you want to be at your best in the NBA, you need NBA coaching/training.
Second, the scrutiny of a player goes up considerably every year he stays in school. If he plans to stay in college and still make it to the NBA, he'll need to have a surefire way to more minutes, more shots, and more responsibility. Being a hyper athletic 8 and 5 only works as a freshman. Unless he turns that into 16 and 10 next year, scouts will rip him apart as stagnating.
Third, there are three to four players joining the team next year that could (probably will) get more notice and opportunity than Davis. Part of that is how good those players are, part of that is the nature of being a non ball-handling big man in the NCAA. Davis staying and playing a bit part on a championship team won't sell much (you can look at the history of Kentucky's players staying past their freshman years).
If Davis has multiple teams saying that they will draft him in the first round, he should probably go. Leaving now doesn't stop him from getting a degree later, and he's more likely to develop into a long-term NBA player by getting NBA coaching. But it's that first round pick that really matters. First rounders are guaranteed two years, and teams are invested in seeing them pan out. Second rounders need to be very clever in the structuring of their contract and at the same time will not necessarily receive the same amount of developmental investment as first round picks.