We have reached the end of an arc which started a year or so ago when Marten first visited the Secret Bakery. Sure, there's likely to be a bit more angst, and discussion in Coffee of Doom (and maybe Elliot(t) will have another word to say) - but Padma's gone, and that story is ended bar a bit of whinging.
So what's next? What new direction might Jeph take with his characters? And assuming Marten remains a/the key character, what's next for him?
If Jeph wants to change direction for a while, perhaps the story of where Dora goes next might be a natural one to follow (she's had a hint of that with Jim, but that's fizzled out); Faye and Angus have reached a more-or-less stable position, which would seem natural to leave on the back burner for a bit; perhaps more of the greater emphasis on AI, and perhaps Hanners, with her upbringing in space. Or maybe back to a bit more music - though I don't expect the return of the indie-based style of the early QC.
And for Marten? Well, there is no sensible romantic interest for him in the current cast, and so any move that way would require more new characters, and maybe another new setting, like tSB was - but Jeph would surely not want to make such a move too similar to the previous one. I discount everyone else for Marten, simply because the only feasible candidates have either been ruled out ex cathedra, like Hanners, or have been around for so long with no spark of interest that it would be unrealistic for something to get going with them, like Raven or Marigold.
(N.B. This is not an invitation to start shipping; the no-shipping rule is not in abeyance for this discussion. Nor are we telling Jeph what to do - just speculating a bit.)