I still don't see the benefit of announcing it at E3 if it's months away from release. They're targeting 20m sold for this fiscal year, so it's in their best interest to have no down time in terms of sales. Keep it as steady as possible.
If it is a new dawn of iteration every 2-3 years I can't see it though. It will need time to explain and convince the masses that this is a good thing and why. The only places they would have the time to do this is E3 or a PS4 reveal type separate event.
Also if the console isn't coming this year as some believe then why are code submissions (gold master?) for Neo compatible titles starting in August? Doesn't that indicate in ~late September they'll be dual PS4/Neo enhanced games on sale and therefore Neo info on game cases?
OK they may leave the announcement until Gamescom but I think that is pretty risky.