Galvanizer on 21 July 2013
Take a look at the history of when past mainline FF games started pre-production:
| Title | Date of starting pre-production |
| Final Fantasy XII | December 2000 |
| Final Fantasy XIII | April 2004 |
| Final Fantasy XIV | May 2005 |
| Final Fantasy XV | December 2005 |
Going off the above dates, I'm pretty sure that FFXVI has been in development for a good few years now. Chances are that it started pre-production as far back as 2007 or 2008.
