I believe that was an error because PD definitely has the PS4 in house so it would be stupid not to start making a game for it. By the time this next installment comes to the series the PS4 will be ramping up so there's no point in wasting time coding for a PS3. On top of that we have the issue with the architecture being totally different between the PS3 and PS4 so it's not like they can straight port it over and working on it concurrently would only hinder the PS4 versions development.