Honestly, I don't think Sasuke has really been all that focused on destroying the Leaf. It's been a 'fun' catch-phrase for him to have - an easy way to vent his frustrations... but for the longest time, he's wanted to make the guilty pay for destroying his family. First, that was Itachi - then that became a huge puzzle, and he shifted his focus to Danzo. He's defeated Danzo, heard Itachi's story, and heard Tobi's story.
Now that he is running out of direct causes for his Clan's elimination, he's left with much more general targets - Naruto, a village full of people who bore him little grudge, etc. And I think he realizes that the idea of killing things over his killed family is really starting to lose satisfaction. He's still angry - still disturbed inside... but I think reason is beginning to take hold.
Perhaps it's also Madara's plan and willingness to go to war (I'm not sure if it's clear that Sasuke understands the goal of Obito and Madara) that has even more heavily tipped the scales. It's now much easier for him to see his own family as being antagonist - of provoking a response.
Though I'm still horribly confused how Sasuke and Orochimaru managed to travel to the Leaf in the allowed time frame of a few hours (unless I missed something) - when it took 3 days by ninja-travel to reach Suna (a relatively similar distance between the Leaf and the north-eastern end of the continent where this is going on).
