The Raspberry Pi 4 announcement claims that the GPIO is pin compatible with the 2 and 3. If this holds true, then the physical connection to the DRAWS™ HAT should be fully compatible.
We have yet to know if Annaliese's kernel driver for DRAWS™ HAT sound subsystem will be part of the initial Raspbian "Buster" release, which is required for the Raspberry Pi 4. The current beta image is based on "Stretch" which does not support the Raspberry Pi 4 (per the Raspberry Pi Foundation), a self built image will be required until such time as NW Digital Radio provides an image based on Buster. Raspbian Buster does not officially release until July 7th.
Status updates will be posted as available.
John D. Hays