As far as we have been told, it looks like that is the case.
From the thread on the Story/Seasons ending,
Unless there is some confirmation otherwise, there is no more content coming as that requires a new update to be pushed. And given that the flash offers (outside of the generic automated ones for runes/scrolls/relics) have been turned off for the entirety of this season and that no more Season passes will be sold, I would place my poker chips on no more new content being released with development of the game being likely finished.
It sounds like they are just going to keep the game going recycling adventures and seasonal events for those that want to hang around. However, for those that have been around for quite awhile there will be nothing more new to experience in PQ3.