Does anyone think that Kasumi will make any kind of appearance in Ninja Gaiden 3??

I believe so.
Team NINJA are being too secretive and want to surprise us just like how we were surprised in NG1's turn of events.

I'm 95% sure she's appearing. since Hyashi himself included her in sigma2, and she had no part of the original NG2 game. so it's a way of "saying look forward to NG3 that I'll be making!" that and there was no reason to force him to add here if it was for no reason, her appearance in sigma two is so brief that if it serves no purpose it can be omitted, and she had no part of the story line of sigma2.
so her appearance in sigma2 is merely for preparing us for a new story line and a bigger part for her in the story line.
if she didn't appear in sigma2 it would make us feel that NG3 is not related to the prior NG, and would seem like a reset rather than a sequel.
if she doesn't appear in NG3, it would mean one out of two options:
1- I wrong or over thinking things.
2- something happened during the planning phase of NG3 for teamNinja to change their plans or abandon them.

lol...I told you before that her appearance was for fan service.
Fan service is just a way of wowing the fans.

Personally I want her in NG3 but if she doesn't appear, I don't care.

do you want her to appear in NG3?

I would like to see her in NG3...

Well not really, I would love to have momiji as a playable character again.