If they had two development teams doing them bi-annually, like Call of Duty, they could definitely pull it off. They'd need to be console spin-offs though or else FF will start having Super Bowl-esque numbers on the end and that ain't good.

Of course there's an issue of making a game of this scale with today's development costs. You really need about 3-4 years for games like this. But there's no reason why you can't have three teams doing it - give one to Kitase, one to Ito, and one to Minagawa. At least 2 out of 3 will be solid games