update...

It's being fairly widely reported that Bono said this at the end of their last concert, which was March 2nd in Buenos Aires:
"Daddy's coming home now - hang on there Sian - hang on there baby diva"

That concert was televised in Argentina, so there are a lot of recordings of it that have been circulating for the past week, and it does seem fairly certain that is indeed what he said (as opposed to being one fan's interpretation of what they thought they heard B. say). Sian is 8 years old. :-(