AMD has committed to supporting AM4 until 2020, but you still have a fantastic upgrade path to the 3950X 16C32T CPU and plenty of RAM.
So I can run the latest 3000 series with my current first gen AM4 board which is great. As you point out though the 16 and 32 core chips might be too power hungry for some boards.
I would love to see an AM4 3600G and 3700G though, basically a 3600 or 3700 with the addition of a GPU chiplet. There are plenty of people out there that could use more CPU but don't need a discrete GPU for work.
As I understand it, they aim the high-TDP parts at the enthusiast/gamer/workstation market where a discrete GPU is just a given, so there'll probably never be a 3700G. Darn!