Depends on the narrative device, Tohaa and particularly Spiral are well set on becoming a hybrid of Alien and Human tech, that would be interesting, especially if Spiral reemerges as a terrorist organisation in the Human Sphere.
I think could be nice if Spiral become in the lore a clandestine rebel organization that comprises/attract many veterans, refugees and dissidents that desert or are in contrast with the regular aliens (CA) and humans armies. And that they will expand better the concept that from their perspective they saved the humanity and their world preventing the El to get the digester.
But I agree with other people here saying that CB regrets to have made Tohaa and Spiral. Unfortunately they also sold less than expected so I don't think CB would want to invest more or try to revamp them. Most probably, as seen recently the effort will be focused on Japanese armies and we will see more and more on this. After all is it more safe and economically advantageous to follow what the customers like more. Money talks!
From a lore perspective Tohaa are a great addition to Infinity, from a sales point of view they are not great, but that is not terminal, a redesign will happen eventually.
Doesn't it seem pretty clear by now that Spiral will disappear from N5 for good? Bostria said they need to reduce faction count, and that pretty much all of NA2 are on the chopping block and will come back either as their own fully fleshed-out sectorial or not at all. That to me seems to spell the end of Spiral Corps.
I think I'm okay with losing Spiral as long as Spiral's main gimmicks (Taagma Sniper, Tri-Core, Kriigel Smoke, etc) get rolled into Tohaa proper. I'm expecting Pheroware to eat a bit of a nerf (whichit should, as it's non-interactive) and this would be a way to inject a bit of power back in.
I don't like that the NA2 will be chopped out and in the case of Spiral will be incorporated in the Tohaa. I think is a bad signal to the people that like to play these mercenary armies and bought the miniatures. I hope that in the worst case they will let them as Out of Production but they will let us the possibility to play them. I already have to swallow the fact that there are clearly factions/sectorials that receive more love from CB in terms of power units (Nomads and JSA just to cite two). And this I can somehow understand and tolerate since they sell more, but please for the players that have other taste let the possibility to enjoy the game with the factions they like.