Sorry for the late reply!
Tackling your last question first, the League of Legends Forums were a challenge to manage, to say the least. Tamat was one of the folks who was tasked with leading the transition from Forums to Boards, and here's what he had to say regarding the rationale for the transition:
- The classic forum technology limits our efforts to make any changes at all, let alone improve the community experience
- The classic forum doesn't scale well and the League community grew faster than anyone expected
- As there isn't a feedback loop within the classic forums to explain moderation actions, moderation continued to become more challenging
- There are a number of security issues with the classic forums, and we aren't comfortable compromising when it comes to security
http://forums.na.leagueoflegends.com/board/showthread.php?t=4909234
I can go more in-depth if you have any additional questions about this or would like clarification for any of these points.
The "Beta" classification is a bit more tricky. In a nutshell, there is plenty of room for improvements for the Boards and there are a bunch of ideas that the development team put on the drawing board a while back. Due to one reason or another, however, development has virtually stalled at this point. Believe me, though; we're talking to different teams across different regions to see what our solutions are with regards to rebooting development in some capacity. While I wouldn't tell you to get your hopes up just yet, we'll continue to explore options to ensure that the Boards remain a conducive environment for fostering the League of Legends community for the foreseeable future.