Unfortunately it is not possible for us to estimate what it is worth, or predict what it may be worth in the years to come.
You need to sit back and hold tight. Free Regs end next month. The further the date from which they were given away free, the more they will be worth. Park it and leave it to rest and see if you get any traffic... traffic means money, money means worth.
But before you do leave it for the free registration year, ask yourself one question... would you buy it if you saw it was available when you actually have to pay for the name?