I think most of here think the game will be of high quality. That doesn't mean it will sell. How many sales do you think will be considered a success for the game? In the end, we all know that many things with the game will live and die based on how well it sells. If you don't have a benchmark for what success is and want one, think about how many sales do you think would prompt Sony to make a sequel and/or be enough to make them think DLC characters are worthwhile?
Believe it or not but the game probably cost them around or more $30 million to make, that's the price of AAA games these days. Although $30 million is kinda low for a AAA game.
If so it was probably all for the rights of the characters...