I don't mind refactoring test support routines in maintenance release. I
said it was too late for 3.3 because the beta period is closing; but it
could be fine for 3.3.1 ;)

As for the way forward, I see three possibilites:
1) put everying in test.support, as a single module (that includes
folding script_helper into it)
2) make test.support a package of thematic modules
3) refactor test.support into a variety of independent modules
(script_helper, import_helper, socket_helper, etc.); a small
test.support providing fundamental features such as TESTFN could remain

My personal preference would be for 1) or 3). But whatever we choose, we
should do it consistently. Having a large test.support + a supportlib
package + some independent helpers is not a good idea.