tox should grow some support for converting/running from .travis.yml files. Via twitter @Marius Gedminas @Jannis Leidel @Donald Stufft all gave useful hints. Projects to look into for inspiration or integration:
I think that generating a tox.ini on the fly could work well. It might make additions of features to tox neccessary. For example, it would be nice to be able to specify platform-dependent extra commands for installing debian packages etc.