There aren't a ton of details out there just yet, but French developer Nadeo announced TrackMania 2 over the weekend. The game was revealed by Nadeo's Florent Castelnerac at something that I'm going to go out on a limb and refer to as "Festival du Jeu Vidéo." Because that's what this public event in Paris was actually called.
The big details here are on the customization front. Track creators will now be able to create objects in 3D rendering software and import them into the game, instead of using the prefab parts that defined the track creation process in the previous releases. A new scripting language, called ManiaScript, is also being built to further help people make wild stuff. The game is said to be scheduled for a 2010 release exclusively on the PC.
Nadeo hasn't publicly released any assets, but some folks on-hand at the presentation captured a bit of a trailer. Here's that:
French-language game site JeuxVideo has more details... in French.