To the OP: only Acoustica knows for sure and they aren't talking .....yet.
Your question spurred some reasearch, though and ironically the best source of concise information seems to be Wiki:
VST 3.0 came out in 2008. Changes included:
Audio Inputs for VST Instruments
Multiple MIDI inputs/outputs
Optional SKI (Steinberg Kernel Interface) integration
VST 3.5 came out in February, 2011. Changes included note expression, which provides extensive articulation information in individual note events in a polyphonic arrangement. This supports performance flexibility and a more natural playing feel. 
In September, 2013, Steinberg discontinued maintenance of the VST 2 SDK. In December, Steinberg stopped distributing the SDK.
The audio inputs for VSTs sounds cool but polyphonic expression would be an awesome addition. As far as the routing capabilities, as of yet I don't think I've ever come close to using all the MIDI channels available to me now and I can't get my head around what the UI for such would look like in VsT3, probably a flow chart?
I don't expect the markets to be flooded with VST 3 instruments or VST3 versions of VST2 instruments soon though since, from what I've just read, there is no easy upgrade path from VST2 to VST3 which means developers have to completely rewrite all the VST2 instruments from scratch and are not all that excited about such a project. Since Steinberg is no longer supporting VST2 the change to VST3 format is inevitable but will be a VERY
slow process. Developers of DAWs and VSTs are gradually climbing on board, but you won't see an explosion in production until there's lots of $$$ to be had.