AMD says: You will be able to. Our current X370s and all the other current Ryzen MBs will work with Ryzen CPUs and upcoming Ryzen APUs -- for at least two or three years into the future.

One of AMD's selling points is that new CPUs do not need new Motherboards. With Ryzen they enhanced that to include their APUs on the same MB as their CPUs. So upgrades and moving components around among one's computers will be fairly easy and cheaper than it might have been.

The exception is Threadripper -- the Threadripper CPU is so large, it needs a special motherboard socket for Threadrippers. However, I assume that today's Threadripper MBs will work with Threadrippers coming out in 2020 or thereabouts.

I'm planning on getting a Ryzen 2800X to replace my Ryzen 1800X -- and just switch it out in my current system (for fun -- it won't be a lot faster -- maybe 10 percent). My wife gets my current Ryzen 1800X -- if all goes to plan.