I'd be more interested in what it takes to support all the major versions with one code base. For example, the only way to get exceptions which works from Python 2.4 (RHEL 5) to Python 3.3 (Fedora 18) is to use sys.exc_info(); "except X as e" doesn't work in 2.4 and "except X, e" is no longer accepted in 3.x. I have no real experience with Ruby to know how hard such support is in it.
I'd be happier if one of Python 2.x and 3.x just went away, but that's not going to happen any time soon and short of splitting the codebase, supporting both can be a pain. Plus, 3.3 now supports namespace modules (which is emulated by straight.plugin for now), so there's another version break I have to be aware of.