Late as well, but my very quick 2 cents:
As long as we can run the tests on released packages, I don't mind where they are.
We have a problem currently in Plone core already though: there are a few core packages (plone.volto, plone.exportimport, plone.classicui, and some others), that are using pytest and zope.testrunner can not run them at all.
This means, that any change on P.CMFPlone that breaks them goes unnoticed.
I was planning to work on it during the Alpine City Sprint, but the testing matrix on plone.meta and plenty of conversations (and breaking Jenkins 
) took that time away.
I will try to get a first working version of a Jenkins job for those packages maybe tomorrow at the tune up day 