I changed the post-slug on my blog a couple of days ago, hoping SE's would just pick up the new page names but it doesn't look like they have yet Will they pick it up eventually? or what should i do? Thanks
Did you add a 301 redirect from the old URLs to the new locations? If not it could take a very, very long time for search engines to index the new pages and drop the old ones. I've done this a couple of times. The first time I didn't use a 301 redirect and the site took almost a year before most of the new pages were indexed and most of the old pages were dropped from the primary index. The old pages remained in supplemental though. In the case where I did add a 301 redirect to the new page locations it took the search engines a couple of months to sort everything out, however they still had trouble with pages that had incoming links from other sites to the old URLs.
Since it sounds like you didn't add a 301 redirect I would say it will take quite awhile for it to work itself out. Without the redirect a search engine could mistake the new URLs it finds as duplicates of the old URLs and get confused. As I mentioned above, when I previously did this and only changed the permalink structure (without adding a 301) it took nearly a year for things to be indexed properly. So if I were you I would add that 301 to help speed up the process of getting the new URLs indexed and the old ones dropped.