That's excluding the Smart division, obviously.
You've certainly noticed that Mercedes-Benz has been dabbling in smaller cars recently. The prime, and so far only, examples include the A- and CLA-Class, both of which are built on the same front-wheel-drive platform. Sales for both have so far exceeded expectations. As such, this now begs the question as to whether Mercedes will build something even smaller. And the simple answer is: no.
In a recent interview with Automotive News Europe, Daimler CEO Dieter Zetsche said that "We had a long debate about whether we should expand Mercedes into the B-segment (smaller than the A-Class) and we decided this is not going to happen." So that puts an end to any rumors regarding a potential Audi A1 rival. However, Zetsche continued: "There is a possibility that Smart could expand into the sub-compact segment, but we have not decided that yet." This is probably for the best. There's a reason why Daimler created the Smart division in the first place.