Pretty sure we're going to be seeing absolutely no major changes after the descent/tunnels/railgun/babblers/weldable doors for a while.
My guess is the new things will introduce a lot of new balancing issues, rage, and will take about 2-3 months just to settle that down... then they'll probably do another xD.
Funny thing is, they're hiring a game designer to improve balance and depth in NS2, so I think Charlie's realizing he needs a bit of help with that...