We're definitely watching how things play out and testing constantly with older versions. Facebook doesn't always roll things out at the stroke of midnight, and so far, it looks like the change has not occurred. When it does, we definitely expect authentication issues with the 3.x series, as it's using the older PHP library from Facebook and doesn't have any of the Javascript updates required by their OAuth2 implementation. Unfortunately though, there's no way to test what the outcome will be before the transition actually occurs.
On the Facebook Developer's group, there's a comment by Cat Lee (FB dev relations) that states "We'll post a blog post with next steps. Not sure if it will make it for Saturday, but definitely on Monday."
www.facebook.com/groups/fbdevelopers/
Once we see any ill effects, we'll likely be posting a status update with what we're seeing (error code, etc) at the top of the forum to stave off too many "It doesn't work" questions.
Hope that helps,
Alex
OAuth - 1st Oct and site still working?
