In a report Kotaku sources point to Microsoft and Sony wanting to extend the generation and launch their next consoles in 2014. Some sources tell Kotaku that if pushed they think their consoles could arrive in 2013.
What it all amounts to is that Nintendo may have a headstart if they are to launch the successor to Wii in 2012 as many reports suggest. And if these sources are to be believed Nintendo will be the only company showcasing a new console at E3 this June.