Artist's comments:
「そろそろ三期出ようぜ」

長門のように　ずっと待ってるから。

"It looks like the third stage is about to appear"?
"It looks like the third iteration is about to come out"?

I don't really get the context here. Is it related to merchandise? It kind of looks like they're opening up a box, and given Nagato's affinity for anime/games/figures, etc. in fan works it seems like it could be something like that.

Third Season possibly?

BarefeetChaser said:
Third Season possibly?

Is there going to be one of those? Because that would be awesome.

And that would make sense as a translation, although I still don't know what the image is supposed to be.

Artist says they've been waiting like Nagato for a third season.

Artist's comments:

(Let's get going on the third season.)

Because I've been waiting like Nagato.

That said, I can find no mention of an actual third season being planned.