That’s the official answer so far. I assume it’ll be similar to the new app transition - at some point you’ll get a pop up in the app telling you it’s time to move to Edge. You’ll probably be able to defer action for a month or so before they force it through. At that point something will happen on the back end to map your devices (zigbee and z-wave at least) to a best-fit Edge driver. If you have nothing but “normal” zigbee/z-wave devices then I would bet that you’ll be just fine, though maybe something won’t be quite as full-featured or work quite the same way as it used to.
The other piece of this is the overall Groovy shutdown. If you’ve installed smartapps from custom code, then that’s another thing to look at that will require rebuilding. The stock Smart Lighting smartapp is also part of that, though there’s more likely to be a solution from ST for anything built in that. If you’re using scenes and routines for your automations, you’re already future-proofed.