Wasn't too convinced, but even if it does come out free on PS+, considering that it's already August, it would have to come out either on September or October, maybe November; and by then the PS4 will be close and when it comes out you'll probably want to spend time there. Not sure if Amazon would lower more than $19.99, lately their sales have been rather sad (the only reason they have this price is because it's a PM). How often do you get to see a relatively new game with good scores around $10-$15 on Amazon? This game came out on March 5, 2013.
That and I read they might make a sequel on next-gen, so pulled the trigger.
I'm not too fond of downloading stuff; my PS3 is one of the first Slims, and Nowdays I have to keep deleting stuff to install new full games (like those from PS+, last one installed is Hitman, had to delete Uncharted 3).