First we have byakugan, sharingan and rinnegan. And now there's this:
Is there a name for this kind of eye which happens to belong to a bijuu?
I was also thinking about the capabilities of each doujutsu (it's nothing new and correct me if i'm wrong):
The byakugan can see through things and is able to see someones chakra system. Combined with highly advanced taijutsu the user can block someones chakra flows. The byakugan itself doesn't seem like a offensive doujutsu, but it aids the user in both defensive and offensive manoeuvres.
The sharingan can also see someones chakra system and from it read someones ninjutsu (hence copy wheel). It's also used to cast genjutsu, meaning can disturb someones chakra flow instead of blocking it. In mangekyou mode it becomes an offensive weapon, with some unique abilities: Tsukuyomi, Amaterasu and Susanoo.
The rinnegan appears so be more offensive. I don't know if it can see someones chakra flow too, but I assume it does. It can move chakra in and out of someone's system instead of just disturbing it, effectively removing someones lifeforce or bringing dead bodies alive. The rinnegan also shows great nature manipulation capabilities.
And then there's Juubi's weird looking eye, which looks like a fusion of rinnegan and sharingan, an "ultimate" doujutsu? By the look of it, it might just combine the sharingan's unique abilities with those of the rinnegan. When I think about the other doujutsu, they show gradations in manipulativeness of chakra that's not the user's own. What would the next gradation be? Expanded range?
I hope Kishimoto will soon reveal more about it's power. Until then we can only speculate about it.
(I might be confused about what doujutsu means btw... is it the eye itself or the things the the user can do with it? Maybe I should call it a new bloodline limit then.)