I've got a watch that is preparing to ship as well (38mm sport white band that I ordered 3:08) but they didn't send me an email about that one. Just the watch that there's been no movement on (ordered 3:04).
So I'm guessing this email is bad news. Apple's way of saying we're working on it but don't expect it Friday.
That's what I'm guessing. UPS has mine in their system (sitting in Mount Juliet, TN)and I didn't get the email. So I'm assuming the first round ones arriving on the 24th didn't get that letter.