In an interview with G4, Yosuke Hayashi from Team Ninja has hinted that there are are characters from the old NES trilogy in the new game which will be available for the Wii U, PS3 and XBOX 360. Could these be Ashtar and Jaquio he's talking about?
Ashtar and Jaquio= Day 1 purchase
G4: Masato Kato was the writer for the original Ninja Gaiden NES games. Does this mean we’ll see any crossover between the two different Ryu Hayabusa timelines?
Hayashi: Absolutely. There are some links – you’ll see characters from those games appearing in this one…
Hayashi: Hmmm, I can’t say yet! But there are definitely people you’ll recognize by their names. Consider they last appeared as NES sprites, however, maybe it’s a bit tougher to recognize their appearance… *laughs*
EDIT - I forgot that DOA Dimensions confirmed that Sonia = Irene!
Yeah, that made me sad. Even though it doesn't fit with the NES Ninja Gaiden at all, and even though it's all kind of pointless to consider, it still makes me sad!
As for NG3...I'm not sure. I liked NG2 as a refinement and expansion of NG Black, but it was still an exploitation of the Flying Swallow technique at its core. NG3 doesn't seem to go anywhere really new, other than adding some grit and tossing in some pretty unconvincing gimmicks (wall climbing, cowering enemies, more QTE-ish combat). It's not looking especially enticing to me, but I'll have to check it out for myself.