Subaru is already a one-platform manufacturer. The current Impreza uses a shortened Legacy platform with Legacy rear suspension rather than the old Impreza platform.
This surely means that the Exiga is built on the Legacy platform - the pictures certainly look like just an updated version of the current Legacy estate / Outback.
It'll be a shame if they don't bring Exiga to Europe and UK - the Legacy and Outback are both cramped, by modern standards, and roomier versions would be most welcome.