I think Titirga will play a future role in the audience's understanding of the greater story/world/metaphysics..
Now, Titirga is a serious contender for my top five favorite characters from the series, and that's from a single appearance in a short story, compared to characters we've followed over five full-length novels. I just think his execution is absolutely flawless. The False Sun's protagonist is really Shaeonanra, but as readers of the series we know too much of him to perceive the man as "good". This is Shauriatas, the Grandmaster of the Consult, the most evil fucks imaginable. Titirga, on the other hand, is presented in a largely positive sense. He's intelligent, charming, pragmatic, and ultimately just kinda badass. He's a Gnostic sorcerer, which we associate with the Mandate and Seswatha, and the Mandate are a rather sympathetic faction considering the moral grayness of the series. However, in terms of the structure of TFS itself, Titirga is really the antagonist. But through the prose, the character is described with such clarity and imbued with a sense of total badassery (the references to him seeming like a stone, something impermeable, almost immortal), that the audience is still held in suspense even after fucking Aurang rolls in. Imagine never seeing an Inchoroi in your entire life, nothing even remotely like it, only for one to stroll up out of nowhere, possessing a ridiculously deep Mark.
Titirga's response to this is a dick joke.
Aside from fanboying over Titirga, my ultimate point is that, no, I don't think he has a future role to play in the sense of still being alive in some fashion, be it physically or spiritually or whatever. I think he's dead and gone. The protagonist Shae (and kinda Aurang) defeat the antagonist Titiriga. However, I do think the character of Titiriga itself, beyond his functionary role in the story mechanics of TFS, is a very important piece to a puzzle that we do not yet possess all the pieces to. But once we do, Titiriga and his characterization (particularly his history of blindness, the "scrubbed" look of his Mark -- which should be intensely ugly, considering his power -- and the whole "grasping of words and meanings that should not be grasped" thing) will all be very relevant. To be honest, as much as I love the character, I kind of like him as being a one-off thing.
And as a nerdanel for the fuck of it: I believe that Titirga possessed, to some degree, both the Meta-Gnosis and the Psukhe, and that this combination of magics will become pivotal to Kellhus's later plans, whatever they are (I'm convinced he will learn the Psukhe eventually, if he hasn't already...another reason we haven't seen his Mark?).