The first Jolla was revealed 6 month before sales because it was the first device and they needed something to keep up the interest and show that they are advancing. Now they don't have that restriction anymore.

If the original plan was to launch near 2015H2, they might have accelerated it because the original HW has difficulties in competition. Also, to get reviews and publicity for newer Sailfish OS versions, they need to launch a new device. I do hope when they launch a new device, it will be available either at the same time or very short time afterwards. Otherwise they'll miss the Christmas season...