I seriously doubt the NBA will change it's rules on the draft, as they have a really good system in place from their point of view. They want to keep costs / salaries low, which the current rules do pretty well.
They do not want to pay for potential. The one and done rule gives them power as it causes a lot of players to do a year of college. Players on average develop more maturity, and also have to prove themselves further before getting drafted than they would otherwise. It also gives them a discount bin, so to speak for players who get injured. Once drafted, they play for below market salaries before eventually hitting a payday based on their market value.
So I don't see the NBA changing. If anything, they would want a 2 and done model to increase their benefits. That means there will be valuable players in college, which means a black market. And it will be around as long as college tries to maintain it's cost model.
Well, changing to a 2 year min. if you go to college would only help the NBA. The Bagleys of the world could go direct and not hurt them much.