Yoshi was supposedly on Ifrit Server and gave some hints on what might go on in Phase 4.. Keep in mind that I found this on BG and isn't completely confirmed yet.
But I will post it here just in case
After reading through the original JP blog that posted that screenshot in which Yoshi-P was answering questions when he showed up on the Ifrit server, I can indeed confirm that he said Phase 4 is one week. As a further confirmation, before he gave the one week date he also said that Phase 4 is 'relatively short'.
A summary of other stuff he said:
- They're trying to get Arcanist ready for Phase 4
- Please wait a little more for the details on how Arcanist works (perhaps revealed in the upcoming Niconico Live Event?)
- Event Bosses implemented in Phase 4
- SLI support implemented in Phase 4
- Male Miqotes (and other races?) will have unique motions when entering baths
- When leveling a second class, you will have bonus exp
- Addressed a bug where the cursor goes funny in some instances
- Adjustments to how (slow/fast) a Gatherer levels
- Adjustments (maybe) to the ease of making HQs from NQ materials in crafting
- An in-game event will be implemented right away after Launch (Bomb Event?)
- The dev team has designed endgame events to outright kill players
- (The Labyrinth of) Bahamut is so long, it pretty much requires players to 'save progress' as they proceed through the dungeon
- No plans to implement a 'your server only' option for the Duty Finder as for now
As per why he came to that decision for the last point, Yoshi-P made a long post about the Duty Finder in which he explains why, so wait till the offical translated response for that.
Credits to Stanislaw for translating.