Normaly even the GMs dont know if there is going to be a wipe or not, the only ones that decide that are the Developers, unless the GMs are the Devs too, but thats not very likely.
They wipe to make sure that nobody uses any glitches or cheats to have an unfair advantage over others. There is no proof, but everybody should know it. I have not seen 1 game that has not wiped after CB yet.
Closed Beta is when they get rid of the Major bugs. Most games there are xp or money glitches that cause people to be insanely overpowered so they need to reset.
In Fiesta they are just doing all the events to keep you interested and return you can't expect to keep the few hundred silver that a few people now have.