Sony has confirmed that it will announce its 'release plans' for the PS4 at its Gamescom press conference.
A note on its website
"We'll kick off the show at 18:00 BST on 20 August 2013 with a briefing to media on our release plans for PlayStation 4, as well as updates on PlayStation 3 and PlayStation Vita."
Note that it doesn't explicitly say 'release date', but it does seem to be implied. Given that we already know the pricing (£349), 'release plans' might also include some confirmation on the launch software line-up and/or bundling. A release date on its own would make for a pretty thin announcement.