I very much doubt that Google plans to revert to any earlier version of the OS. They are taking us into the future, not the past. They try to fix any current problems with the present versions of the OS.
What problems are you experiencing with your S4? Have you tried a Cache Partition wipe? It's good practice after a system software update, and causes no loss of personal data.
Try it, and if you've still got problems, get back to us.