I believe you will find the below information quite useful. It comes from someone very close to BMW and a member of Germancarzone. To summarize some of the key points:

- apparently the new BMW Z4 E89 will launch in December
- BMW is also looking into the possibility of an M Z4
- Efficient Dynamics BMW Z2 Roadster, read hybrid

But here is the information, unedited:

With the new BMW Z4 Roadster (launching in December) forgoing a classic roadster soft top and instead using a folding hard top configuration.
Much of the discussion is focused on how much the weight of the car will increase with the now folding hardtop.
Although the use of lightweight materials on key areas of the car do not satisfy the curiosity of many.

Although brought in to prop up Z4 sales and originally a project put on hiatus when the E85 was in development. BMW brought forward the Z4 Coupe as a more performance focused model than the roadster.
Because of the introduction of the Coupe , Z4 sales increased and with the Z4 Coupe proved as a successful product for BMW, that BMW have green-lighted a Coupe version for production.

A feasibility programme into the investigation of an M model for the Coupe only has also begun with the project now being treated with priority now the CS programme has been cancelled .
If approved and M model of the Z4 Coupe will possibly inherit the V8 from the M3 and usual M features such as Carbon Fibre roof.

With Z2 BMW are aiming at the compact Roadster class and possibly a Z2 Coupe could feature as well. BMW’s big push for a Compact Roadster is simple under Efficient Dynamics BMW aim for the Z2 Roadster to be the first hybrid BMW Roadster in production utilising BMW eDrive with BMW wanting to continue with what has started with the MINI-E and continue towards the BMW brand and eventually over to Rolls Royce.

[source]