Do me a favor, assume Elane is Kumori.
Assume Elane is still alive.
What does that mean for the Dresden Files and the future.
Specifically (but not limited to) the Paranet is being managed in part by Elane and signs point to the Paranet either replacing the White Council or merging with it. If Elane is Cowl's loyal apprentice and has been shaping the Paranet she will absolutely have been shaping it to replace the White Council and join Cowl's Circle (black council). This will do a LOT of damage to the forces of good (Harry).
How else is Elane positioned to cause problems and what kind of damage could she do with the Paranet?
Why are we not assuming Elaine is alive? Last she was seen was helping the Paranet.
Even so, even if she went "missing", I wouldn't necessarily assume she was dead. Too much writing potential in the character - and unfinished business with Harry for sure.
If Harry learns Elaine is Kumori, it will only add to his trauma. Given Harry's history...that makes it more likely.
I am not sure I agree that she is shaping the Paranet into some sort of weapon, except perhaps in terms of information gathering (which is powerful enough in it's own right). Not to mention, she clearly has the names and locations of the members (which gives her plenty of power over them, and could sell them out or have them eliminated if she chose).
See, the thing about Elaine is she is Harry's foil in some ways. She is so like him yet more pragmatic. Harry is almost pathologically driven to protect his ideals. Elaine is far more pragmatic about hers. Which is another reason why she might be Kumori. Elaine might see that the best way to protect humanity and ensure its future is to work with Cowl, to "end death" as Kumori put it. But she is also rebellious. I wonder if she is as under the thumb of Cowl as we think...Kumori chose to save someone she didn't have to, and while it furthered Cowl's aims somewhat, she could have far more easily simply raised some zombies or spectres. She chose to try and save someone, and Harry noted this. Kumori is an idealist, but also a pragmatist. Elaine seems quite similar. My personal theory is that Elaine is Enthralled in such a complex series of spells she hardly knows she is a thrall (this was explained by Bob when discussing how Enthrallment works in Blood Rites I believe, where Harry specifically likens fine Enthralling to what Justin did to Elaine...the second book Elaine shows up in - a long-term hint). This of course is lends further weight to the whole Cowl = Justin theory, given Justin was the first to Enthrall her.
Further, I think Elaine would likely be trying to warn Harry and reveal herself in the process. But it would cost her. I think Harry would be further torn between trying to save her (Harry's biggest weakness is his white knight tendencies) and being angry at her. Long term I suspect he probably ends up killing her like Susan, or she dies to save him. I can't see her surviving the series. She might help him kill Cowl though, so there is something in that potentially.