Wait and see is the name of the game.
From what I've seen most of the clean, easy ones have been upgraded.
Some of the ones I've seen that have not been upgraded...
Mine - SAB with hidden address BUT manually merged with G+ before we were told SABs should not merge.
SEOs??? Mine and a few others I know of are not upgraded. SEOs don't show in Google search so maybe we (and other business categories Google does not deem as having local intent) were put on the upgrade back burner?
Listings with hidden merged dupes.
Multi-location businesses.
Possibly, I'm just guessing, listings that have dupes or other data problems.
I'm guessing on some of that and drawing some assumptions. But I just suspect there are listings that got put in the "difficult" bucket and those are the ones (mainly) that have not been upgraded yet. Then again, that does not rule out listings that are fine that she just has not gotten around to yet.