It destroys the visual flow of code and for what? To signify a global, constant, or Enum? Is that really so important? I don't think so. I think the all caps style has out-lived its usefulness and needs to go the way of the dodo.
The last time I saw all caps used appropriately was in a YouTube comment where some guy was ranting about the communist Jewish banker conspiracy to control the world. In that case, all caps clearly communicated to me that the person was a frothing lunatic (thought find the idea of communist bankers intriguing).
Currently PEP-8
prescribes all caps for constants and uses the all cap variable "FILES" as an example in a
different section. It also appears to be the defacto-standard for enums (based on the
documentation)
I don't think it's necessary to make any breaking changes. Just pep-8 and (of less importance) spurious documentation examples.