Well, technically I think its in a slow decline. Since joining 1.5 years ago I'm seeing parts vendors slowly die off, and I don't remember too many new ones. However, I think this is a gross oversimplification. Many of the vendors that have been dying are ones that never really did a good job to begin with (Kaotic, DTec Tuning). Some of the vendors are die-hard CDW27 fans (Cougar and Contique) that will be with us until the bitter end. People like Buckshot are a huge asset for us, and there are companies like some of the exhaust manufacturers that seem to do a good job despite the cancellation of our cars.
Eventually, though, as more and more Contours/Mystiques are junked you'll see demand for parts (OEM and aftermarket) drop, at which point it just won't make fiscal sense for some companies to make products for us anymore.