In a new interview at Game Watch, Final Fantasy XIV Producer Naoki Yoshida laid out some new information about upcoming game patches and revealed that the first details about the game's next expansion will be shown during this fall's FFXIV Fan Festival. While it won't be a direct reveal of the expansion, Fan Festival panels will provide more information on the upcoming 3.4 and 3.5 patches, both of which will start the process of moving to 4.0.
According to the interview, Ishgard probably wouldn't be the setting for the next expasnion and Yoshida indicated that "it's a bit of a sensitive topic". It will, however, be the opening to the next chapter. Yoshida said, however, that revealing more than that would provide too many spoilers.
“I believe that we’ll see the big changes starting with Patch 3.5,” elaborated Yoshida. “Similar to what we had in Patch 2.5 and 2.55, which I believe was a big pivot.”
You can read the full, translated interview at Silicon Era.