I think that the information about the predicted birth date must be known by many people, even if they respect Fed's desire not to say it.
But maybe they go a bit too far about the withdrawal.
Actually you can never be sure about the date of a birth : if the baby is born 2 or 3 weeks before (I hope not), the fact is that Federer might maybe take part.
Anyway there's a press conference in Montreal tomorrow : maybe we will know a little bit more
Well, actually there is a rumour that the birth date is around Montreal. Probably that's where all the speculation about withdrawal comes from. It is likely that Fed has already made up his mind about whether or not to participate, but usually this kind of information comes from his official website. So we just have to wait until official announcement (if the is one).
Why there is no official information about Ancic's withdrawal? At least I cannot find it.