Well, everything is speculation to be honest. The 'Discontinued Post' said a lot without saying really anything...

1. Primals, we know they will be roaming and controlled by the Company that takes them down. What we DON'T know is if there will be 'easier' versions of the primals for storylines and small parties to kill...I kinda doubt this as the achievements will be gone for the clears, but who knows. If the Garuda and Iffy extreme parts of the relic questline REQUIRE killing the Roaming Primal...lots of people are gonna get screwed out of Relics if they aren't in a large, competitive Company... but again, no one knows what's gonna happen.

Basically, if you like having 7/7 weapons on the 3 primals... DON'T turn them in for seals until 2.0...when you know what's up.

2. In the original post on the lodestone from the Devs on this topic they hinted they are still working on a way to display any achievements you earned that are no longer in game in your Lodestone History. I take this to mean, that currently, all old achievements no longer will show UNLESS they solve the problem.

3. Using FFXI and the Wings of the Goddess expansion as a reference, the old dungeons will probably remain, BUT will be 'dated' somehow...like have damage, rock falls that closed off sections, something that makes them the same, but different. Like how Citadel was damaged and worn out in normal FFXI and expansions but in mint condition in the Wings of the Goddess expansion as it took place years BEFORE the main story.

4. Faction Leves...have no idea other than they will be changed a fair bit. But that could just mean how you earn them to how they are done to what you get to what type of battle they are. Nothing was mention about loosing the Harliquin, Templar or Buccaneer Achievement though, so I'm gonna assume we will keep many of the old leves somehow.

5. Nothing was said about not getting the skirmish achievements post 2.0. Based on this, I'd say skirmish remains in game...now whether the rewards will remain the same...who knows.