How long after a patent gets a FINAL REJECTION does it appear as such on Google Patents or before the final rejection is made public?
As of now (10/2014) google patents never directly shows a final rejection or any other status change regarding an application. What they re-publish is the USPTO publication of the application. It is not a "living document" like a web page, it is a fixed thing like physical book.
At the same time an application is published by the USPTO its entire history and future are available to the public. To see the complete record look the application up in the USPTO's Public PAIR database. Then select the Image File Wrapper tab. In most cases that means the public can know anything that happens the day it happens, if you look it up every day to see if anything happened. If an application gets rejected before it is published (either an accelerated examination or a non-publication request), that rejection or other action will not be visible because the whole application is not visible.
Also, a "final rejection" is only final until you pay more money and file more paperwork. Abandoned is the status that means it is dead - even then an applicant can petition for revival under the grounds of unintentional.