I'm not staff there, but I can shed some light on this as a player there. The policy is that they slowly introduce new series during certain chapters and acts (ie Chapter 1, Act 2) as the grid and plot focus(es) shift around.
It's had some pros and cons, but I think it's ensured several games' plots don't start out of the gate at the same time and compete with each other. Also, some plot items, like WA2, are already being dropped in hints. I hoping it'll have the side effect of also allowing new people of feeling able to jump in without having to be there at the MU* opening, too, but that's just my theory.
As for the one other place I've been on:
Battle Fantasia: Been on there on and off. If you like magical girl anime and the whole aesthetic of it, give it a try. I couldn't really get into it after a while, but that was more me than staff's fault.