Arch Linux has switched to Python 3 as default for some time now and it's not much of a problem. It all depends on how the Ubuntu packagers manage the change. I expect things like wicd to break when Arch made the change, but everything worked smoothly. For my scripts, I just make sure my python symlink to version 2 is always ahead in my path, so that #!/usr/bin/env python always gets v2. Although I should also be changing them to call python2 for scripts that cannot switch to 3 yet.
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