There will be some hardware acceleration – but there are a lot of changes for Raspberry Pi users. If your system is working, then you may want to hold off on upgrading until Pi support matures further.
You can take a backup of your system, try Kodi v19 and if not happy, downgrade easily enough. We will keep older images on our website for the forseeable future.
This isn’t a Kodi issue. The whole point of this new approach (supporting V4L2/GBM) is to define a standard that will allow newer devices to be brought up more quickly in the future. The Pi 4 is a very new device which wouldn’t support the MMAL/GLES stack in the same way as before, so the Pi team have made the technical decision to move all support to this new stack from a multimedia perspective, and it does make sense in the long term.
It will all work eventually, but it might take a couple of years to get feature parity.
This doesn’t apply for Vero users – v19 will actually bring a number of new features and improvements as our new video stack is ready for release.