Expansion, new race question.

I know some of the content in the new expansion you can do/use till you complete the main quest line.

But what about the new race, is it going to have to eb unlocked or will I have access to it day one?

you should be able to make an au'ra day one.

Not everyone would be switching with Fantasia. A lot of people would want an Au Ra character to always be Au Ra. A lot of brand new level 1 characters are going to be created as Au Ra, and it wouldn't exactly be very feasible to need to complete the story before you even create your character.

You do need to complete the ARR storyline before going to Ishgard (and I believe any of the new regions surrounding it), and since that's where you can unlock the new jobs, those are going to be gated by the story as well. But the Au Ra race should be available as soon as you get the expansion (or as soon as Early Access starts if you've preordered).

So, of the things we know, there's:

Gated features:
New Regions
New Jobs
Flying Mounts
Main Scenario continuation

Non-gated features:
New Race