Final Fantasy XIII has been in development for over five years, has involved hundreds of staff and has cost the publisher a ton of money. So you can see why there'll never be another Final Fantasy game like it!
Speaking with Sony on the official European PlayStation blog, the game's producer Yoshinori Kitase and director Motomu Toriyama have said:
If you consider that during Final Fantasy XIII's development, at peak time the team consisted of over 300 people. It was a huge team, plus it took a several long years to get the game finished. So, if Mr Wada meant that we would never make another Final Fantasy title with the similar number of people, taking as long as FFXIII did, we would agree.
Obviously in the future we want to be much more efficient. Having worked on XIII, we feel that we have got much better at making good games for high definition consoles. In the future our teams will be smaller and more effectively run.