SE has already announced more plots and wards in existing areas, and apartment style housing is coming after that;

January Live Letter, 4th Question.

Q: Auto-reclamation for housing starts this month, but can you tell us if there will be any future additions of plots?
A: We'll be increasing the number of plots for existing housing areas in Patch 3.3. After we expand those areas, we'll add apartment-style housing in Ishgard areas afterwards, starting with one apartment-style building which will hold about 512 residences. We’re also planning to make chocobo stables available for use to residents of apartment-style housing. Gardening patches are still proving somewhat difficult, but we’re currently developing new “planter pots” that will allow gardening.

As per demand, we are also looking into the prospect of increasing the number of indoor furnishings which can be placed in residences.
Note, that in this answer the original Japanese language used the term 'Mansion' to describe the building housing the apartments. I think that because they want this new type of housing to be roughly equivalent to small personal houses, the apartments will be two level Maisonettes - which fits very well the 'Mansion' concept in the original Japanese.