Not really sure how to title this question.. anyways to the question If I have linked to sites and the update resulted in my site getting PR5 but the sites I am backlinking from drop alot then how does that affect my site in the future. Or would my site only get a good PR if the linking in sites remain high too? Noob question I know but Im curious
Naturally, the btter the site you are linking from, the more link juice (and PR) your site will get. If the sites you are linking to drop, you may take a PR hit; but why stop backlinking in the first place? Keep working on your backlinks; you cannot control what happens to other sites...
I really don't bother PR of backlinks, as long as they are coming from relevant reputed websites. As natorob said, you can't control the situation but this is something which you don't need to worry about.