My hunch is that the minimum fare too would be made rs 10 once the state elections are over. But yes, what you said is always is a possibility.
Also if u have noticed, big stations have separate queues for PF tickets and also have PF vending machines. For a person to save rs 5, he has to be willing to stand in the crowded unreserved queue. Many might not do that and just buy the PF ticket.