You can't update a major version and expect things like this to not change
(What I mean is: sysadmins are aware of this and won't "just" upgrade to a new major version without considering such factors - at least they shouldn't do that ;) )
Hard to decipher what you mean. Maybe you want to say, that is already the default, but as this is obviously wrong you probably want to say, that Python 3 is kind of default now. Which might be true for new projects, but this doesn't have anything to do with the default env for servers. So maybe you did already messed up your server with a python version default change and you want to express that this can not happen to you anymore.
Ubuntu already switched from Python 2 to Python 3 and not many people feel "messed up" by this.
Python 3 is the only Python pre-installed on current versions of Ubuntu. All Ubuntu system utilities that use Python use Python 3. You have to install a separate package to get Python 2.
