Here's something from Tetsuya Nomura:


Originally posted at RPGamer
On Final Fantasy VII, Nomura stated that the chances of a sequel were unrealistic. Since Final Fantasy X-2 was built mostly off the engine of its predecessor, it was fairly easy to quickly produce a sequel. However, the much older engine of Final Fantasy VII would be unusable, and the game would have to be built mostly from scratch. This would require the development time and resources of a brand new Final Fantasy.
So I don't think FF7-2 will be made for a while.