"These are increasingly complex books and require immense amounts of concentration to write. Fans really ought to appreciate that the length of these monsters is equivalent to two or three novels by other writers."At the same time they are written by a guy who is doing convention tours, book tours, closely working with the HBO adaptation of his books, doing the ALS Challenge and nearly hit the edge of the pool where he was at, but is only able to write on his desk AT HIS HOUSE!!
Do you see what this delay means?
It means that the Adaptation will catch up to the books and is LIKELY to go in a different direction than GRRM intends thanks to the latter taking his sweet ass time to finish his saga. Seriously, HBO will finish the series long before GRRM finishes the seventh and hopefully final book!