The BBC news item states...
"On digital terrestrial television (Freeview HD and YouView), BBC Three HD and CBBC HD will use capacity on the BBC’s existing HD multiplex, which has universal coverage of UK homes. BBC News HD, BBC Four HD and CBeebies HD will use new HD capacity, which will extend to cover 70 per cent of UK homes by the Wimbledon Championships in June 2014."
So everyone should have got BBC3 HD and CBBC HD yesterday.
But BBC4 HD and CBeebies HD will be rolled out as "new HD capacity" becomes available in your area. (70 percent of UK homes by June 2014).
So - depending on where you are - BBC4 HD could take a while.