In the recent FFXIV Letter from the Producer Livestream, you can see some features of the rest of the Endwalker patches. The Trust System will be expanded to allow you to carry recognizable characters along with dungeons in older content.
Beginning with Patch 6.1, the popular Trust System feature will allow more players to adventure with famous NPCs in older content, regardless of the progression they have made in the main scenario.
This allows you to complete the main scenario dungeons and specific trials while venturing solo and gives you the option to queue up with random allies. At this time, sufficient FFXIV Gil can help you deal with all kinds of difficulties so that you can go further in the game.
The current Trust System lets you play with allied NPCs but not other players in specific dungeons in the Shadowbringers and Endwalker expansions. You don’t need to wait in line for a dungeon to complete to progress the main scenario. Many of these NPCs are characters you're familiar with from the adventures in Eorzea and beyond, which includes Alphinaud and Alisaie.
This launch of expanded Trust System-capable dungeons will begin with A Realm Reborn in patch 6.1. The next patches will implement this feature in Heavensward and Stormblood dungeons.
The FFXIV team mentioned that specific NPCs will appear in specific dungeons if they make sense in the current story, but the developers will provide more details in the future Letters from the Producer and MMOWTS will track the relevant information.
All players can look forward to trying out FFXIV's Trust System, some for the first time, along with patch 6.1, expected to be released in the coming months. Players who have already upgraded to Shadowbringers and Endwalker expansions can use the current iteration until the Trust System expands.