Since this never came up in this thread - What's your opinions on the proposed 20 year old age limit that's being introduced in 2016?
I say introduced as I expect it to be this way:
NBPA: Yo Silver, you guys are making so much cash, share some of it!
Silver: My owners really like making profits! But we can give you 55% instead of 50% BRI. In exchange we want the age limit!
NBPA: Deal!
My opinion is a little bit split. I think he's right that it would boost the quality. But it would hold back a couple top tier talents an additional year in which they could get hurt. But then at the same time they're already forced to go 1 year to college. So it's not like they're not being forced to take a risk on their health already once they turned 18.
Since I'm the math/statistics guy I took a look at the one and dones since they were introduced in 2006.
In 2006 2 freshmen were drafted in the first round(Tyrus Thomas(4th) and Shawne Williams(17th)) - both busts.
2007: Teams selected wiser in the deeper 2007 draft. 6 freshmen were selected in the lottery, and only one of them was a bust relative to the draft position(Brendan Wright at 8th). One was injured so I don't wanna judge that. Mike Conley #4 is a reasonable pick who took a little longer to get acclimated in the league. Hawes(10th) and Thad Young(12th) are good value for their selections as well. Past the lottery it's different. Javaris Crittenton(19th) is in jail and Daequan Cook(21st) is playing near Stuttgart in Germany.
2008: We've got 7 lottery freshmen but with mixed results. Beasley was obviously a mistake even though the talent was always there. I don't think college would have changed his situation, since student athletes mostly aren't really attending class when they don't want to. OJ Mayo at #3 was obvi a HUGE MISTAKE(in the GOB Bluth voice from Arrested Development).
Jerryd Bayless at #11 and Anthony Randolph at 14 were also mistakes that might have been avoided if they were given more time in college.
The 2nd half of the first round included JJ Hickson at #19, Kostas Koufos at 23 and Donte Green at 28. Pretty good quality if you forget about Green.
In 2009 only 2 lottery freshmen were selected. Tyreke Evans at #4 and DeMar DeRozan at #9. De Rozan obviously right now looks like a steal, while Tyreke Evans never could develop a jump shot and the change in the culture of the game from hero ball to team ball was his neck breaker. In the 2nd half we got Jrue Holiday at 17 and BJ Mullens at 24. Mullens wanted to return to school but his family urged him to enter the draft as they needed some cash. His career has been underwhelming but for a #24 hail mary on a shooting big it wasn't that bad. He just was very hyped out of high school.
The next year 7 freshmen were drafted in the first round. High lottery picks Wall, Favors and Cousins are very successful, while Xavier Henry(#12) was never as good as some thought he might be in part due to injuries, opportunities and probably also his attitude

He's still fairly young and if he can stay healthy and the games with the Lakers weren't a fluke he can still get some checks!
Bledsoe(#18), Bradley(#19) were big steals a couple years later. Daniel Orton(#29). Let's not talk about Daniel Orton.
The freshmen class of 2011 is devastatingly BAD up to this point. 4 lottery picks, 3 busts over the duration of their rookie contract. Kanter(#3), Thompson(#4) and Knight(#8) have needed a lot of time to get going. Very good argument for a two and through rule.Tobias Harris(#19) also needed time to scratch his potential, as did Cory Joseph(#29). Also there was the first freshmen second rounder with Josh Selby at #49. Who's Josh Selby?
In 2012 a total of 8 Freshmen were drafted. 5 in the lottery, 3 of them very productive relative to their selection. AD, Beal and Drummond offered very above average rookie play. Especially when you factor in age. But AD and Drummond have almost unique bodies in the league. Beal is a very skilled shooter.
MKG at #2 and Austin Rivers (#10) were absolutely not ready for the big show. Outside the lottery we've got Mo Harkless who offered a very solid rookie season on a big tanking team. On a real team he'd been buried on the bench. Tony Wroten at 25 was also a non factor to the extent that he was traded from Memphis this summer but he really bounced back with the big opportunity he got from the Tankadelphia Sixers. Marquis Teague(#29) looks like a coattail surfer and another guy named Quincy Miller was drafted in the second at #38.
If I compare this group to the group that took their time, I can't really see a huge difference in long term success. Most very talented freshmen went their way and just as many current stars have stayed at least 2 years. But there's a group that strengthens the argument. It's very rare to have rooks that offer starter level qualities and left as one and dones, when you consider the talent. Most need an extra year to develop their game/mature.
Also you have cpt coattail type of situations but that's solely on the team to take a chance at a very young prospect who simply was another part of a winning team.
So for the overall quality of the game the two and through makes sense IMO with very few exceptions. So you let the sure things suffer because other guys manage to cash in on their (over)hype. That's my conclusion if the rule happens. I also like Silver's D-League suggestion, but that would mean people have to actually go watch these games, you need high quality basketball teachers and also fair salaries.