Eren Mckay posted on Google+ a link to a post on feedthebot.com where they spotted the updated Google Webmaster Guidelines. The new guidelines were reportedly removed, because they were mistakenly posted too early.
Someone took a picture of the post with the details of the changes. You can see the screen shot over here.
Some of the changes call out more specific spam methods and a lot more talk about using rich snippets but not spamming them.
Overall, it seems they have tried to simplify the main guidelines document but add more hyperlinks to more help documents that explain the guidelines in more detail.
I am not sure why Google pulled it down or if this is 100% legit. But I do trust the source of the content.
Forum discussion at Google+.