We saw the spot where the 3,900' zip line will end. I'd imagine the construction would take some time -- it's a huge distance to cover, and the braking system alone would take a while to implement.
My son and I are considering a return trip to Aerial Treetop Adventures around Aug. 5 -- day after his 16th birthday -- so we will look into it. The original plan was to try out the long zip line. But we're patient...
Looking forward to another day on that ropes/zips course!