These are rumors, easy bait for clicks. I'll happily eat my words when this comes to fruition, but at this point is there any evidence Apple is actually interested in doing this?
The MFI program largely makes money because Apple control the lightning connector interface and can thus be the gatekeeper. While I don't like it personally, it does make some sense to me the mfi program might want this feature for a USB-C iPhone and future iPad models.
Like others, I suspect it would be data access only limited to the certified devices - any old USB-C cable will likely still work to charge. This likely satisfies the EU charging law changes and lets them keep much of the MFI revenues.
That the MFI program exists is frankly evidence enough for me to believe Apple would do this - they sell many more iPhones than iPads, and the change can be incorporated into future iPad models.
Apple is notorious for not breaking out revenue specifics in its public financial reports.
What source are you using to determine that MFI revenue is "significant?"
While sure there's some extra margin on those cables it seems the cost of MFi certification seems to be more than just a penny per cable.
Now, iOS supports ethernet-over-lightning, so you can plug an ethernet adapter and have it connect to your router. But it is illegal to make an accessory that would "integrate" an ethernet adapter. If you make an accessory, it has to go through the MFi protocol.
Here is an example: if you take a DJI drone and connect the remote controller to your iOS (lightning) device, it goes over MFi. It would be illegal (as per the Apple ToS) for DJI to use ethernet over lightning there.
Now go to Amazon and look for a use case where you can’t find a perfectly suitable non “certified” device.