It seems like the Playstation 4 release date has varied from 2010, 2011, and 2014. The official PS4 release date has not been announnced by Sony but there is no doubt that there will be a system succeeeding the PS3. The Playstation 3 has yet to reach its peak due to heavy competition but when game developers begin to overlook the blu-ray flaws, the best games will be available on the PS3 and Playstation 3 sales will rise. Resources have been primarily focused on the PS3 at present but once the Playstation 3 is where it needs to be in sales, the available resources will begin to turn its attention to the development of the Playstation 4. We will see the PS4 sometime between 2010 and 2020. Some articles have even mentioned that the PS4 might not even need discs. This would be fine if it was possible for you to download large game files in a short amount of time. But who knows it seems you can do almost anything on the internet nowadays.

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http://hubpages.com/hub/PS4-Playstation-4