Fuel economy standards are forcing all the manufacturers. Mercedes' line actually would be fine if they actually sold the A- and B-class in the US, but since they don't want to dilute the brand here they've got to move the CLA. And it's not just the US. The reason so many cars are now 2 liter is because of Chinese standards. Sadly what is likely to happen is that all the premier brands are going to build a bunch of cheaper cars or get gobbled up by big companies to survive, if they haven't already been for other reasons like Bentley, Rolls, Ferrari, Porsche (actually this one gobbled up VW, however that worked), Audi, Lamborghini, Bugatti, etc).
Hopefeully BMW and Mercedes won't have to pull off something as sad and pathetic as the Aston Martin Cygnet.