There's a good reason to change back. There is now convention in place, and Arch's approach is obsolete.
Well, the answer is that this is a silly discussion. Arch is doing what Arch is doing because Arch is intentionally forward oriented, sometimes to the detriment of backwards compatibility with the old school (and yes, a distro not having a symlink for python2 is at this point nearly 5 years into being "old school").
Arch's change angered many in the Python community, and broke a lot of code. That Arch refuse to adopt the established convention, because it would involve admitting a mistake, shows a distinct lack of professionalism.
Well, until developers that do their work on other distributions start getting bug reports as a result of Arch's unexpected naming convention. Should someone outside of the distribution expect Arch to change so that their software works there? No. Should Arch expect outside developers to adapt their code to work on Arch? No. Honestly, I'd expect the kind of people that Arch attracts to be used to dealing with little snags in operation, and for them to just dive in and fix it on their own.