Four seat convertibles should have soft tops. Hard stop.
Even MB knows this and the CLK and the newer E cabriolet have soft tops. Porsche sort of cheats on the 991 with hard horizontal surfaces, but cloth over the whole thing and no hard structure on the c-pillars. Plus calling a 911 a four seater is sort of cheating.
The good news is that the 2er and 6er should remain soft tops, so folks that want a folding hard top can have it in the 3er and those that don't can have it with the other two. It's nice to have choices, and I suppose BMW is one of the few offering both formats.