Well, as for the population overall, last time I checked FF14 was around 5 million subscribers. The game is quite alive but many peoples felt like heavensard re-used a lot of ARR stuff.

You'll mostly be focusing on finishing the MSQ(of course), the anima weapon quest(Relic equivalent) is out and is quite a grind, there is the exploration mission which send you with a bunch of people in a big instanced zone combining fighters AND gatherers and finally the first Heavensward's 24 man raid have been implemented.

So far the expension is enjoyable if you can avoid the salty comment on the forum.

If ya need to know something just let me know!