If you look at current pricing of first-gen Ryzen CPUs, they have become ridiculously cheap compared to their launch price with the Ryzen 1700 available for as low as $160. That's probably where you can expect the Ryzen 2700 to be at 6-8 months after the Ryzen 3xxx' launches.
This is a long time to wait if you are eager to upgrade right now, but the rewards are quite considerable. Also, RAM and SSD prices are still dropping, might save another $30-40 on 16GB RAM and 480+GB SSD by buying a few more months from now too. If you are planning to replace the HD6850, I'd recommend waiting for Navi even if only to see how much down-pressure it'll put on GPU prices, I'm hoping for a significant shakeup in performance per dollar.