I'd be perfectly satisfied not buying one every year? Maybe take a year off, and polish up your fucking engine, eh, Ubisoft? Yeah, I've played them all, and bought each new one (though, I still need to grab Liberation), either on day one or a few months later. I've liked most of them, and only hated one (*coughrevelationscough*), even if it was a place I'd love to explore.
You know what I don't like about the series, despite the consistent, surprisingly high quality they put into them? The movement. It's still sticky as fuck. They really need to change how high profile prioritization of running works. stopping a high speed pursuit because he wants to dry hump a wall is absolutely aggravating. But the stories, settings, and graphics have all been pretty damn impressive, especially considering that they crank these things out in what has to be 11 month cycles. If they took even a few extra months and tweaked the mechanics for the protagonist, instead of adding a lot of other stuff that varies from fun to useless to tedious micromanaging, I think I'd be a lot happier.
That said...we're already seeing diminishing returns. Revolutionary France and something like the Meiji period in Japan are the only two settings I *REALLY* want to dive into. Anything too modern features too many guns for my taste, and the best thing about AC3 and AC4 has been the lack of 15th century super snipers and a focus on the blades again, rather than the shittastic and uninteresting guns. Unless they had the balls to let us go back and play as first civ. That would be worth it.