Loughton Spur (?) is the man who seems to have his finger on the pulse.
Think it was him who found the Haringey document which outlined the proposed construction schedule (a few pages back). According to that document, construction of the northern end of the NDP (the supermarket) will begin in the spring / summer (today's announcement confirms that); and construction of the stadium itself will begin next year, with the two thirds complete stadium ready for use by the beginning of the 2015-16 season and the stadium and podium fully complete by the beginning of the 2016-17 season. Finally, construction of the southern end of the NDP (residential, college, health club; health centre and shops) will begin in 2016, though I don't know of any date for completion of the whole development.
Of course, all of this assumes that the club can secure loans on acceptable terms and a naming rights deal that is equally acceptable.