I think some people are seeing the word "change" and freaking out.
In essence, a better word for this would be "upgrade." The core of the changes are a switch from vB3 (the software that the boards currently use) to vB4. It's not going to change any of the core functionality of the boards, that I am aware of.
Before you ask, yes, I did try the new boards when Morrus posted this in Meta. Yes, as far as I could tell everything here now was there. Ah, the benefits of reading and posting in Meta!
Now, my understanding is that with vB4, there are two primary "changes" in addition to upgrading the architecture.
The first is an increased emphasis on social networking. Does this mean the boards are unusable if you don't partake?
No. If you only read and post (like I mostly do) then you can keep on doing that without utilizing any of the social networking stuff. We pretty much do that now anyway; a lot of that functionality exists right now on the boards. However, those that
do want to utilize the social networking aspects of the board can do so, and again based on my understanding those will be more robust and integrated.
The second is actually an increased stability. AFAIK, a lot of the board functionality that is currently hacked into the system will be more integrated. This should lead to less problems with those systems going down and requiring effort to fix Now, they're directly supported by vB.