That assumes that killing Iris is really what Savitar did/does/will do as opposed to what everyone thinks happened. I have no idea how it could be a fake out, but... It might actually make a more interesting story.

But that may be because I've been thinking about an anime/manga series where the villain does something of the sort.

Or maybe the Iris we've been seeing recently isn't the real Iris?

I don't know the storyline makes so very little sense.