As far as I know, AMD completely discontinued their AM3+ line of CPUs, and focused on APUs, and as great and innovative as the new kaveri are, 7850k does not even come close to fx 8350 provided you use a GPU.
So is AMD planning on developing new CPUs that will be stronger and with more than 4 cores or are they all into APUs now?
Far as we know, its full-steam ahead on the APUs. I imagine that the goal is to get APUs with 6+ cores at some point; there's just not enough die-space for them to accomplish that yet though.
AM3+ is almost certainly end of life. That is not to say though that an overclocked 8350 won't serve high performance for a few years. I usually go 4 years between CPU upgrades; I could easily see myself sticking with this chip for 5 - 6, unless something that just blows it out of the water in price/performance comes along.