Alright, after a lengthy brain storming session over this issue I've finally decided to go ahead and said yes, I think you should open the Beta to the public.
My reasons for this are quite simply productivity. You can go silent but this may not necessarily mean that you are going to achieve as much as you would if you got vital game play feedback from a whole load of gamers. A mass Beta release would reveal all sorts of problems and possibly even suggestions, such as map errors, balance issues, model bugs, weapon problem and the like. As well as this making EX a more known mod, because currently it is hiding in the lofty archives of Terra, would attract a great deal more attention and this would not only mean gamers, but people who are willing to model, map and possibly even code for you!
Furthermore a period of silence could deter much activity and even rob yourselves, Emperor forbidding, of the will and appetite to continue with the perfection of this mod. However if you come back to plenty of healthy feed back then you have something to get right to work on, instead of having to locate the game issues yourself with many more, small scale Beta tests and then go on to the process of correcting them. An outside word could be very good for this mod and veteran gamers aren't just good at fragging people but they also excel at noticing the traits of a good game and also the flaws.
So, in my opinion, yes, you should release the mod in the form of a public Beta.
