There's zero reason for a game to be announced this far in advance. There's also zero reason for a game to take more than 5 years to develop, unless you're dealing with mismanagement and lazy/unskilled developers.
Seriously, though, games don't need to be "announced" until you have a release date and you're sure you're going to meet it. Maybe, in extreme cases for HUGE titles, you announce the game a year before release, but again, only if you are sure you're going to be able to release at the end of the year.