The last piece of interesting information comes in the form of a little chat Shacknews had with Valve's Robin Walker. There's too much to just quote one part, so allow me to list the highlights!
- New maps and achievements are already being worked on for each class.
- They're targeting around 35 new achievements per class.
- In addition, they're looking at a way to obtain unlocks without strictly using the achievements.
- The TF2 team tests out community made maps every Tuesday and Thursday. Next up on their plate? cp_redstone.
- They next want to try out a map where the cart (ala: Goldrush) is actually large enough that an Engineer can build on top of it creating a moving fortress.