I think it's likely that the title simply refers to the official announcement of winter's arrival. We're due for Sam arriving in the Citadel; it would make sense if he was present as they send white ravens out across the realm. Perhaps we'll see one arrive at Castle Black just before the White Walkers breach the Wall?
More generally I think it will be something of a misdirection for most of the episode. I think we'll see lots of characters have moments of triumph, or personal accomplishments, only for this reminder of the coming threat to sting us right at the end.