Would be interesting to see them switch places, but doubt Lilith could be reborn as a Angel. Everything she did to Sanctuary during D4 campaign was pretty deplorable. Meanwhile, Inarius may physically be an Angel but his motivations no longer align, and he acts more like a demon - motivated purely by self interest.

I think the prophecy actually hinted towards this and it's a popular interpretation:

Then came a spear of light, piercing Hatred's heart

At the end, Inarius is operating solely off hatred. He wants to destroy Sanctuary just to get back into Heaven, and Lilith points out they don't care and do not answer him. He then shows anger towards Heaven, asking why the other angles still forsake him. Lilith then takes the spear (from her lower abdomen) and plunges it through his chest. The use of Hatred as a proper noun is just a red herring that Inarius fell for, assuming it referred to the daughter of Hatred.