Mr Duffy over at id has made a .plan update with some more info on Team Arena:

Quake III Arena has always offered the most capable, technically sound, and best looking game platform around, and now that we have added a whole host of new functionality ( much of it at mod team requests ) mod teams will have in their hands the most complete game production toolkit ever and some really cool toys to play with. They are going to have the ability to produce a complete ass kicking, commercial company spooking, single/multiplayer player game experience. I am looking forward to seeing what people do with the all the new stuff.

Hinting at a lot more to come. He also mentions they'll be looking into the reports of reduced framerate, which is a plus for people with lower specs machines (like me).