Well, Crate have dropped hints of possible storylines already.
19th April 2019 dev Stream:
gachibass_chechnya_kavkaz : Could you share with us what’s gonna be in the next expansion/GD 2 in terms of storyline/lore, at least a bit?
I’m not sure I should really talk about that because I’m not sure when or if it’s going to happen. I mean I can give you some ideas of threads we might pursue. For example there is the whole thing with the Emperor, the capital, with the Sun (son?), Ulgrim seems to be a special guy too. The Witch Gods seem to have gotten their way - what does that mean for the future of Cairn? What will happen to the future of Kymon’s Chosen? That Sigil?
12th July 2019 stream:
Any plans for the NPC found in the Fleshworks to make another appearance?
So his story is not going to finish with Forgotten Gods, his story is for things beyond. Which is more of a sequel.
Also hope that we’ll get that Loyalist Pack #3 for GD. If you won’t let us throw money at you for the town builder yet, then let us do so via another Pack please.
And still waiting for that Crate story to be finished and released @medierra The outstanding goal from the KS; given GD is now “done” might be a good time to wrap that up as well. 
Then you can start writing the sequel. 