Yes, you'll be able to build and drive vehicles you've made in-game, as well as import vehicles made in external programs like Blender. I would like to eventually add different vehicle classes, like: wheeled vehicles, helicopters, planes, physics objects, boats and a class similar to the magic carpet.
I'm not too familiar with how Roblox handles them, but I'm hoping to give bricks certain properties (similar to Banjo Kazooie: Nuts & Bolts) - i.e. you can add thrusters for flying, objects to make the vehicles float (like for a seaplane or seacopter), etc.