I must say that some of this discussion sounds bad, but I don't think the note on the website must be read that way. All it says that once you do FP+, regular FP isn't available to you. I believe that all that means is that if you are using an RFID for FP+, your ticket will not work in the FP machines.
While it's possible that it means more than that, it doesn't have to. So, it is possible that the only change in park is that instead of sliding your ticket in a machine to get a day-of FP like you do now, you'll tap your RFID on the a machine to get a day-of FP, or, even better, you'll go a central kiosk or use your smartphone to load a day-of FP. The system could be set up to know what park you're in (the App already knows this), offer you the available FP times for each location, and let you pick one, informing you as the paper tickets do when you can get another.
In other words, I don't see FP+ as necessarily meaning that only the pre-book style "choose a limited number of experiences" are available. It could by that you get the pre-booked limited number PLUS whatever number of day-of FP windows as you would be able to get now -- you'll just do it through your RFID/smartphone, rather than slipping your ticket in the machine.