Apple will find a way to monetize mouse support....no doubt. There will be a proprietary Apple trackpad that supports iPadOS gestures, and it will cost over $100......count on it. It might be integrated into the Keyboard case, which will become more expensive, or it will be stand alone accessory or both. But, Apple can’t pass up an opportunity to make some money off of this feature.
They did the same thing with keyboards and pencils. For years, you could use third party BT keyboards and stylus on your iPad, and you still can. But then, Apple created the proprietary Keyboard Connector and Apple Pencil chip......voila, $200 keyboard case and $100 pencil. A proprietary trackpad is a no-brainer accessory for Apple.