I'm planning to have all the WFB at BoLSCon still under the 7th Edition rules, for the following reasons:
#1 List Submission is due before the new Edition is released. This means people with good leaks will have time to tune and prepare lists for the new Edition, whereas those who do not would be flying blind.
#2 Very few people will have a command of the rules in under 3 weeks. I do not think people want to play learning games at a GT, and we would have to drop the number of games, lengthen the time limits, and probably have longer days just to get a standard 5 game GT done.
#3 The Pairs event would be even harder to figure out than the GT. Wierd rules interaction games are fun if you're familiar with the rules, but with unfamiliar rules, it seems like a whol lot of pain.
#4 The staff requirement would go up dramatically (by a factor of 3x or more) to deal with the unfamiliarity. And, to be honest, the judges would make more mistakes. Neither of these are desirable.
Those are my thoughts on why to stick with 7th Edition this time around. I'm interested in your thoughts, too.