I imagine it's more likely to be an April Fool by the person who gave the "Unconfimed report" to Sky than Sky themselves. Surely they know how little sense of humour the butt of the joke would have about that, they might as well do an April Fool about a terrorist attack in London or the Pope dying.
EDIT: But then we get stupid "unconfirmed reports" and equally crazy real events happening pretty much every day of the year, it's no surprise if it's one or the other that's just fallen on April the 1st.