I posted a GMod 10 news update over at the GMod site. Here's a quote!
Work continues on GMod 10.. we?re getting pretty close to it being finished. Pretty much everything is coded in Lua in GMod10 - you?re probably thinking ?so?? but it really excites me to think of how much people are going to be able to mod it now. It?s going to be insane.
We?re pretty much done implementing the GMod ?Sandbox? mode, there?s just a few things to do and then that?s finished. Then we?re adding a few new/old gamemodes to show off the new Lua implementation (which will also serve as examples for the coders out there).