You have to realize "Square" isn't a collective, it's made up of several teams made up ofpeople. the Tactics team was mdae up partly of Ex-Quest employees (Which is why it's similar to Tactics Ogre)
The team, after tactics, sort of split. The ones that remained in square went on to do Vagrant Story (which explains the heavy Tactics references) and the actual battle mechanics guys (the quest guys) left.
They're next game is to be Hoshigami for the PSX.
It will be on american shelves this fall, and it looks almost EXACTLY (style-wise) like Tactics.
For more information, look here
http://www.rpgamer.com/games/other/psx/hoshigami/hoshigami.html
http://psx.ign.com/previews/15172.html
http://www.hoshigami.net