Could changing PageRank cause the number of pages indexed and SERPs positions to fluctuate?

Assuming no on-site changes and also assuming no significant changes in competing pages, is it possible that some pages could go totally missing from SERPs and others seeming to drop out of site all the way back to the last page when nothing appears to have changed?

Matt Cutts, in the same Infrastructure Status update said as much when he wrote,

“If you used to have pages in our main web index and now they’re in the Supplemental results, a good hypothesis is that we might not be counting links to your pages with the same weight as we have in the past.”

Beyond that, if PageRank can influence which index a given page is in, Main or Supplemental or whether it is even indexed at all, if a given page's PageRank were to decrease for some reason either as Matt mentioned or even one or more inbound links no longer existing, it would not be too hard to imagine the page moving from the Main Index to the Supplemental Index or dropping out of the index altogether.

Read also this forum with topic: What more could I do to improve my SERP?

fullnotes: cass-hacks.com