I don't see why 65 would be so unrealistic when you consider the following:
Depth
Last year, our team would struggle with an injury to any of our starting 5. Not so much that Sheed, Baby, or TA were bad, but it would push fringe NBA players up the depth chart. So instead of Shelden Williams being the 5th big he would be thrown into part of the rotation and become our 4th big. Same happened when Pierce missed 10 games or so.
To start the season we currently have Erden, who is better than Williams, as our 5th big and, barring injury, most likely will be headed to the NBDL once Perk returns. Robinson is an upgrade over last year's Eddie House. Maybe not the 2007-09 version, but House's game, and shot, has really fallen off. In addition, perhaps West isn't the defender TA is, but at least he allows Doc the ability to play him alongside Rondo because of his shooting ability.
Philosophy
I'm so glad that Doc has made it a point to play inside/out. I feel that a key to us losing a lot of games was our inability, or unwillingness, to play off of post players. This made our offense very simplistic and more often that not we didn't capitalize on our size advantage over teams. Sheed was unwilling to post up, KG didn't have the health or confidence to, Perk doesn't have the skill-set, and Baby is too small. Now, KG looks more confident being in the post, Shaq lives there and JO has a nice up game. Also, while Baby didn't grow over the summer, his mid-range jumper looks much improved and this will allow better spacing for whichever big he is paired up with.
Guys, let's not forget that we also play in the awful Atlantic Division and play NY, NJ, Toronto, and Philly 4 times each. If we go 15-1 or 14-2, something that's pretty realistic, this means we have to go 50-16 to reach 65. Are either of these things so unbelievable to accomplish?