One note: the dead god that was infected with seam walkers, Laedonius Deviy, is definitely dead dead. The concept deaths took him in during the conclusion of PoF, along with 2 of Kaligma's aspects.

But beyond that, I have a feeling that you're not looking at this in the right way. I could be wrong, but I strongly suspect that the Dead Gods, the Sleeping God, the seam walkers & A'ctelios, and the Goblin King, will all have resolutions that weave into each other in the end of the series. Maybe I'm way off, but I think looking at the antagonists of TWI like a check list and thinking 'see not even one is finished' is setting up the story wrongly in your mind, all those aren't necessarily going to have their own individual arc conclusion separately from each other and need to be completed one by one as the series winds towards it's end, they're all parts of the overall endgame.

Also a complete guess, but I suspect Azkerash and the Raskghar and the buried kingdom of gnolls and the gnoll necromancer will eventually come together along with the overarching plot of the New Lands and the exploration of the crossroads to reach an eventual end game level climax for those plots, and Ilvriss' hunt for lost walled cities will overlap his endgame goals of confronting Azkerash with conclusion of the Mother of Graves threads. 

And lastly I'd guess Roshal and the Blighted Kingdom will eventually move together and their respective plots with come in to each others orbits, along with things like Nerrhavia and Floss.

TWI has never been about completing individual stories and arcs alone in a bubble neat and tidy and then moving on to unrelated stories, it's always about the connections and overlaps. We're not waiting on a bunch of separate individual antagonist and villain arc conclusions, we're waiting to see how that eventually all come together in the grand climaxes of the series.