You can use DX format optics on the upcoming m4/3 Speed Booster, and an example is shown in our white paper using the Nikon 35/1.8 DX lens.
However, its important to note that the m43 Speed Booster will have the same 0.71x reduction factor as the NEX version. This is a bit less than the optimal value of 0.75x you would want for converting DX lenses to m43 format. As a result, DX format lenses will appear slightly wider when converted to m43 via a Speed Booster than they do on a DX format sensor.
For many lenses such as the Nikon 35/1.8 or Sigma 30/1.4 this is purely beneficial. However, its possible that a few ultrawides may show some corner vignetting since we are revealing more of their image circle than was originally intended.
Another thing to keep in mind with the upcoming m4/3 version is that some DX format ultrawides have a non-removable lens shade. Due to the aspect ratio mismatch such a shade can cause vignetting along the long sides of the final m4/3 image.
Of course, if you are using a Black Magic camera these two issues go away because of the slightly higher crop factor
At some point we may decide to build a special 0.75x Speed Booster for adapting EF-S and DX optics to m4/3, but we are starting out with a 0.71x version because it gives a full stop speed increase and it works better with FF optics.
The m4/3 version uses different optics than the NEX version mainly because we were able to improve optical performance by optimizing for the smaller format.