Well, there is constant references to a 'Crystal' in some of the trailers, so who knows? Maybe a 'Great Crystal' zone could fit into ARR without too much trouble.

As for areas I'd like to see, I can't say I'd like to see any earlier zone really in ARR - I'd rather SE come up with original zone ideas than simply recycle old areas for 'fanservice's' sake. But that's just my personal opinion.