MotorTrend.com is speculating about the details of the new BMW 3-Series fighter from Cadillac (which everyone is calling the ATS).
They are suggesting that the drop-top version will go with a fabric roof vs. the retractible hardtop that is popular with BMW (in the 3-Series) but is not by any means universal (witness the soft-tops from Audi and Mercedes). The advantages of a fabric roof are easier packaging as well as keeping a heavy top mechanism and its adverse impact on handling dynamics (by keeping the center of gravity low) in a car that is going to sell on its superior handling.
Interestingly, in the MT article, they are suggesting that the previous rumor of the 6.2l V-8 making it into the ATS-V with 400+ hp is not a done deal. There may be V-6 with forced induction in the cards (with similar output) to bring better fuel economy if not lower weight (all the forced induction hardware will likely make a V-6 of this type practically as heavy as a normally aspirated, OHV V-8 like the 6.2.
Expect the ATS to reach production in a couple years as a 2014 (later for the V, coupe, and convertible).