Everything Blizzard has said points to sooner than that. They stated as recently as this week that they intend to release expansion content quicker than they have in the past. If MoP were released November 2012 that would put it 2 years after Cataclysm, which came 2 years after Wrath, which came 2 years after BC. To release XPac content 'quicker', they would need to release before Fall 2012. I'm sure they will. I actually think we're very close to the alpha/beta.
Also they said recently that the version of MoP played at Blizzcon was 'far into development'. Another clue that MoP is closer than some think. I'm sure they'll hit their Q2 target. Then they'll hold Blizzcon early 2013 and announce WoW X5 and Titan.