Another bit of news from the Detroit News Auto Insider (from the same article that's mentioned below):

Another variant is the Mini convertible, whose release has just been confirmed for summer of 2004. Both a 90-hp and a 115-hp model will be available at launch. A 163-hp Cooper S model follows later. The roof folds down in just 10 seconds and sits on the rear like the VW-Beetle cabrio. It will be built on the Mini line at BMW's Oxford plant.

This is the best photo yet. I don't know if it's the car or my mind playing tricks on me but somehow it seems like it's starting to look more like a proper MINI.