Well this is what we got:

Items to Become Unobtainable
The following items will become unobtainable:

* Dated items
* Weathered gear
* Weathered weapons and tools will remain obtainable
* Items obtained through seasonal events
* Rewards for achievements that will become unattainable in FFXIV: ARR,
such as the Dalamud horn
* Items obtained through events associated with the coming of the Seventh Umbral Era,
such as over-aspected clusters

Link