The likelihood of any ancient text being recovered from "lost" status at this point is very very low. Not impossible, but very unlikely. Fragments of just about anything can still be discovered, especially in papyri, but finding works in their entirety (or significant portions of them) in the modern world is exceedingly rare, especially for "mainstream" stuff like lost epic poems, lost books of Livy, lost Athenian drama works, etc. This is primarily due to how the texts we actually do have came down to us, which was overwhelmingly through the manuscript tradition: copies of copies of copies of copies stretching back into the 9th century CE and beyond, which was still 700 years (and up) removed from the time of writing of those ancient texts. Works that did not get copied in this way generally do not survive, period. Some works come to us by sheer chance and by the tiniest of margins. The poetry of Catullus, for instance, survived in a single forgotten manuscript by 1300, and that "original" was gone by the 14th century and only survived in three copies.

At certain points in this transmission process, there were those who were particularly interested in "rediscovering" moldy old tomes to save their contents. Petrarch is a great example. He spent a large portion of his life scouring the damp basements of European churches and monasteries looking for texts. Petrarch and those like him in other periods were generally very thorough. That means that, in the 21st century, it is very unlikely that a given country church in Tuscany has a sealed attic loft filled with undiscovered manuscripts. Certainly it is possible, but as a general rule we can assume such places were thoroughly "checked" centuries ago.

On the other hand, certain places became vaults for such manuscripts. The Vatican library is a great example: it is positively stuffed with manuscripts, and access to the library is famously tricky to acquire, especially for non-specialists. It is definitely possible that the Vatican library possesses manuscripts that have not been properly examined for several centuries, any one of which could contain parts or the whole of a "lost" ancient text, especially palimpsests (ancient texts which have been scraped off the velum page to make way for a copy of the Psalms, or whatever).

Regarding the Villa of the Papyri: yes, it is certainly possible that lost ancient texts are here. From what we've seen thus far, the collection seemed to mostly involve philosophical texts, and there are thousands of lost philosophical texts from the ancient world. The odds of getting one particular lost text from this list of thousands of possibles is exceedingly low, even if we want to find a particular philosophical text. Finding something non-philosophical is even more rare. There are thousands and thousands of lost texts from the ancient world, and those are only the ones we know about.

So in short: is it possible to find, specifically, Titanomachy just in general? Very unlikely. Is it possible to find Titanomachy specifically in the Villa of the Papyri? Also very unlikely.