The CMake port on FreeBSD is in the hands of the KDE-FreeBSD folks (since KDE was an early adopter), and generally it falls to me to do the CMake update while Tobias is still wrestling with Plasma and Raphael massages Qt 5.9 into our way of building. 3.10 was released five weeks ago, and it took a while to update the port.
It doesn't take long because of CMake -- they're great, the code builds flawlessly, and there has been a real effort on the part of the KitWare folks recently to absorb our downstream patches so that we have less work in future (During the delay packaging CMake 3.10.0 Kitware even put out 3.10.1, which re-started some processes). It doesn't take long because of new FreeBSD-specific features in CMake -- you can now use CPack to create native FreeBSD packages, just in case you don't want to go through the ports system or poudriere.
Nope, the problem is the 2000-odd ports using CMake. These generally behave, but every CMake update brings with it some ports that suddenly don't build. So I spent a day on things like openvsp and scalapack, which fall over with 3.10 (and didn't with 3.9). The causes of these failures is diverse; sometimes bad local CMake modules that don't add all the right linking flags, sometimes bad C++ code, sometime stuff that has nothing to do with CMake at all but just happens to be newly triggered, and therefore my problem.
CMake 3.10.1 landed in the official ports tree with r457041, just before Christmas.
Naturally, there are some cases that fall out after an update, that are not caught before the update is committed. I'm told that FreeBSD on PowerPC doesn't have a C++11-capable compiler installed by default, so I'll need to massage that a little. Boost 1.66 came out very shortly after CMake 3.10.1, and that leads to new kinds of breakage. I've spent a half day compiling and re-compiling ceph, a distributed filesystem, trying to get that to work. It's amazing sometimes how shifting one brick can bring down a whole house, and how we ever built the house in the first place.