Perhaps you could argue that the Python3 language could have changed it's name and "left" the trademark and reputation behind for some other random people to take over. But a stronger argument would be that the reputation Python has earned over the last two decades "belongs" to the ongoing team who built and supported it for way longer as version 2.X than they needed to and who've now been releasing it as V3 for over a decade.
If "people are still using" Python2, nobody is going to stop them. Nobody it deleting all the copies of the source code to Python2.7 or revoking any of the rights the granted when it was released:
"PSF hereby grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce, analyze, test, perform and/or display publicly, prepare derivative works, distribute, and otherwise use Python alone or in any derivative version" (from: https://github.com/python/cpython/blob/2.7/LICENSE )
It you're uptight because the PSF owns and protects the trademark to the name "Python" where used in relation to a programming language _that they wrote and gave away and granted you extensive rights to do whatever you damn well please with their source code_ - that's a totally unreasonable expectation on your part.
Spend two decades building your own reputation for intelligent and responsive language design and stewardship, then walk away from all that reputation by allowing random people to piggyback off it, then get back to me and tell me how that's actually how shot should work... Guido and his team have put the hard yards in. They've given you pretty much free reign to do whatever you like with their source code. They are not only under no obligation to allow you to call what you do with that "Python", but they arguably have a responsibility to ensure that people who expect a historical level of stewardship and "benevolent dictatorship" of the language called "Python" are not mislead by people other than them using that name to continue to promote old and discarded technology and design decisions with any assumption that those new people deserve any of the historical reputation that "Python" implies.
Get over the "Wah! I can't use the name Python! I'm being oppressed!!!" childishness. I, for one, do not want _you_ specifically, and people like you in general, to fraudulently trade in the reputation that the Python trademark would bestow on your work if you were allowed to call it "Python".