Since the end of the Detroit Auto Show this year we've been getting more details on the coming line of M Performance vehicles from BMW. Taking their spots between the standard line and the true M vehicles, examples like the 2012 BMW X6 M50d and M550d xDrive (neither of which will come here) get tweaks developed by the M division under the hood, in the cabin and around the exterior, mated to traditional items like torque converter automatic transmissions instead of dual-clutch gearboxes.
Their arrival here is planned for the 2014 Detroit Auto Show starting with the M235i coupe (the coupe and convertible versions of what we know now as the 135is, pictured), and when that happens a report in Car and Driver says M Performance models will replace the "is" trim as the next-generation BMWs are being introduced. That would mean cars like the 335is become the M335i sedan and M435i coupe and convertible. Initial M flavors right now are expected to include the Z4, 1, 2, 3 and 4 Series.
The original announcement from BMW claimed that the M Performance vehicles would receive "exclusive engines," but the C/D report suggests that might not be the case. The mag also says that we'll see the M335i or M435i as soon as next year.