>Gmail will remain free as long as email is expected to be free by users.
This was also the expectation of G suite users. Forcing non-business users onto a paid business product which didn't even exist when users signed up was not the expectation. The original question should be looked at from that perspective. How long until Google creates a business focused Gmail plan and forces any user who uses their Gmail for business onto that plan. That could be done with a simple change in terms of service as well.
I would expect there to be more pushback and revolting if Google suddenly said you can't use the free Gmail product for business. I can't even guess the number of contractors, artists, coffee shops, Etsy stores, food trucks, etc that I've personally interacted with that are using Gmail, Yahoo, and AOL email accounts for their business.
I also couldn't imagine this happening, just think it is a better way to frame to conversation and understand how G suite users are feeling right now. There is a counterpoint though based on what you said, the large number of business users also means a larger business opportunity for them. The G suite to workspace transition has been 10 years in the making, you could imagine spreading the outrage over a longer period of time and many users not even noticing it is happening.
This was also the expectation of G suite users. Forcing non-business users onto a paid business product which didn't even exist when users signed up was not the expectation. The original question should be looked at from that perspective. How long until Google creates a business focused Gmail plan and forces any user who uses their Gmail for business onto that plan. That could be done with a simple change in terms of service as well.