It's not just the lack of toolbar PR update, everything seems to be treading water. Things just don't seem to be getting updated as quickly as normal. That's not only new sites and the sandbox effect, it's also true of some established sites.
The impression I get is that Google is reducing the updates of the main system to a minimum so that they can parallel run a big update behind the scenes.
Pure idle speculation, of course, but my spider sense is definitely tingling...