Drivetrain choices will include either a naturally aspirated or twin-turbocharged 3.0-liter inline-six, found in the 328i and 335i, respectively, with an M version packing the M3's V8 and a carbon fiber roof. In addition to new front and rear fascias, a lower roofline and a ducktail spoiler, BMW is expected to employ a handful of stylistic differences to separate the Z4 coupe from its folding hardtop sibling. For 2009, BMW is expected to drop the soft-top Z4 and only offer the folding hardtop.
The rumored Z2 is currently in the works and could be available in both coupe and cabrio variants, and equipped with some form of BMW's EfficientDynamics system. The 1-series-based two-door is expected to be powered by either a naturally aspirated or turbocharged 2.0-liter four, and there's also talk of a hybrid version utilizing BMW's eDrive system.
UPDATE: BMW has put together a Dexter-inspired teaser site for a new model set to be revealed in 19 days. We'll know what's up on December 14th.