Ubuntu developer Barry Warsaw provided an update today on the removal of Python 2 from the desktop ISO. He explains that it's in the printer space the cause for still keeping Python 2 around... "system-config-printer is already itself ported to Python 3, but it transitively depends on Python 2 through the chain of python3-smbc to libsmbclient to samba-libs to libpython2.7. So the real problem is fully porting Samba to Python 3. Ubuntu is not the only distro converging on this bottleneck."
But in not being able to get Samba out of the picture or on Python 3 for Ubuntu 16.04, Barry is proposing an alternative to demoting the python3-smbc to a "Suggests" for system-config-printer, which would allow the desktop ISO to drop the Python 2.7 packages from the desktop ISO. However, on the downside, Ubuntu would then not be able to automatically detect Windows printers on a default install. For trying to ease that potential pain with Windows network printers, they may add a button to the printer dialog for installing the packages -- and Python 2 -- back after the default install.
Those wanting to learn more about this potential final step for getting Python 2 off the Ubuntu desktop ISO, see this mailing list post.