> We will charge fees in the future perhaps

Hope you're going to be clear and upfront about this to your users, not hide it in the small print.

Because otherwise you're going to have lots of justifiably pissed off people posting severely negative reviews everywhere the day the paywall goes up.

Bait and switch is never a good look. You might get away with it if you are excruciatingly clear and upfront about it, I still wouldn't encourage it though.