It’s not likely that Dorico will be able to import or export Cubase projects directly in the foreseeable future. The reason for this is that, like most applications’ file formats, the Cubase project file format only really makes sense to Cubase itself. For Dorico to read Cubase’s project file format, it would have to have most of Cubase’s code inside it; and while Dorico does share some code with Cubase, of course, in order to provide playback, that shared audio engine doesn’t deal with Cubase project files.
However, we hope that over time we will be able to build a more streamlined workflow for getting data back and forth between Cubase and Dorico than only using MIDI, even if it does involve an intermediate file format of some kind.