Not the bestest of news, especially because of "old threads" sake. But i guess you had no other choice...
Few selfish wishes, though: don't change the things over-dramatically - it's easier to come up with the "perfect" results in many small updates than in one "Big one". That said, don't change the color layout or the logo for example, because those things are your "brands" for many years and you wouldn't be doing a favor to yourself, if for example, new forums would look
like this.
As for avatars, they're fine until too big and distractful, so i think this small increase in size won't be noticeable that much. I also hope there won't be an option to put pics into the signature. Forums like these become galleries, and not the place to read things.
I also hope the main page of the site won't be changed for the "worse" - because you were on the right path. It didn't feel "sterile" like a Linux desktop, but not too much crowded with info and news, either.
Also, we were planning on starting the comm. playthrough, what would happen if we start it before the new forums? It's not possible to "move" the content of any single thread?