They did this last year in December for me and I called to complain when status was not carried over (missed by 3 days). They did grant Diamond status for this year and reminded me 40 nights needed to make Diamond for 2010. Had this been later in the year I'd argue the point again, but this eMail was way too early to believe.

I do give them points for customizing each email with name and remaining nights needed. It could have been a generic message showing no concern for customer service.