Originally Posted by Westlo
There's also the final 3 novels to be animated, I think only 1 of the "3rd season" has been released so far. Also this being Nisio it's guaranteed to get spinoffs of some type, and considering the popularity of this series a fair chance they get animated too...
Perhaps it's a matter of not wanting to get too far behind. They could take 7-8 years to animate 5 one-cour seasons, which could end up with Monogatari being past its shelf life, I guess. Knock six of the books out at once before 2013 closes out and they can get to the third season by no later than early-mid 2015.