The next console from Microsoft will have an E3 2013 Announcement with a Holiday Launch or even early 2014, and Sony should launch around 2014.
Develop claims that several projects are already underway for the new Microsoft system, including a Fable game at Lionhead internally named 'Fable Next'.
The site says data from multiple "sources across the industry, from processor chip manufacturers to middleware firms" confirm that Microsoft is getting ready.
"A trusted source connected to the matter" told Develop that several of Sony's 16 internal studios have stated work on PS4 game concepts that could enter into full production if given the green light.
The site claims Sony has yet to finalize the console's technical specifications and that the PS3 successor isn't expected to launch before 2014.