
While it's not about the Persepolis Fortification Archive, it is interesting nevertheless. Until now, the most recently discovered Old Persian text was from the Persepolis Fortification Archive:
Stolper, Matthew W.; Tavernier, Jan. From the Persepolis Fortification Archive Project, 1: An Old Persian Administrative Tablet from the Persepolis Fortification ARTA: Achaemenid Research on Texts and Archaeology, June 2007.