It's really odd that this seems to be more prevalent now than it was a few years ago, but maybe I just didn't notice it...
For the last few years, though, it seems like there have been spates of series coming out around the same time / same season of different years that are very similar in their themes and artistic directions. But, I've heard that anime is usually produced almost on an ad-hoc basis, being created as it's aired more often than being completely pre-planned. Also, I would think that different shows take different lengths of time and start at different times...
So, I guess my thought is that this is more a reflection of the zeitgeist in Japan, rather than just a marketing tactic. Although, it seems to move a lot faster than the general themes that show up in western TV.
Or maybe it's just that the same tropes that have been used since the 70s are evolving to become new tropes, with a larger field of extrapolation? Kind of like how Eva changed mecha anime, and is still reflected in anime like Code Geass, despite being very different story structures and characters.
Or maybe I should just drink more coffee!
