With alternate worlds coming in 5.0, they could use this concept to their advantage by having parts of other worlds bleed into Hydaelyn. In GW2 there were leyline anomalies which was a neat thing.

I don't think that SE wants to introduce new open world elements because it is different and they like to hide content behind instances. This WAS fine since FF14 was its own thing, but now people are done playing GW/GW2, WoW, BDO and other mmos and are moving to FF14 as the last successful surviving MMO besides TESO. With potentially millions more players making their way to FF14 with different levels of expectations, and hopes for this and that, it would only make sense for FF14 to adopt certain successful/familiar elements from other MMOs to help new players bridge and stay active.

I personally really enjoyed how GW2 did "FATEs" which build up events for other events etc... You sometimes see it in FF14 but very rarely.