I think you are confusing several different things:
1) "switching to Python 3" -- if by this you mean making /usr/bin/python point to python 3, that will never happen on Ubuntu (and probably most other distros that aren't Arch.) They've stated that even when everything that relies on python is moved to python 3, they will follow PEP-349 and keep python 3 at /usr/bin/python3. /usr/bin/python will only exist when python2 is installed and will always be python 2.
2) "removing Python 2" -- obviously, they won't retroactively do this to an existing LTS release. It'll probably be first done in a regular release between now and the next LTS release (it was targetted for this LTS release, but not everything was ported, so currently both python 2 and python 3 are used.)
3) Making Python 3 a "first class citizen in the Ubuntu world" -- it already is.