Reason For Page Rank drop:
When I started to concentrate on this blog in the early of this year the page rank was 0.Then I started implement all SEO techniques and that time google rolled out page rank update but my page rank did not increase(February 2012).Then I started to concentrate more on this blog and started building quality backlinks and at the next update (May 2012) the page rank increase for 0 to 4.During the August update the PR remained the same but now it dropped to 3.The most probable reason for this drop is after August page rank update I stopped building backlinks(Quality backlinks),and the number of sites linking to this site remained the same and also the number of outbound links from this site increased,so this is the reason that the page rank dropped.As my internal pages are linked properly page rank of those pages remained the same and also this helped the new pages to reach PR2.
Future Page Rank Expected Dates For 2013:
It is clear from the previous updates that Google is updating PR once in three months,so the next expected page rank to be around February 2013.So do not get disturbed by this current update,keep blogging and get ready for the next update.