I'd bet on $30 like FFXI expansions usually were. It'll probably be hard to find a physical copy this day and age, but they'll probably make them at least, possibly some super ultra deluxe ones! Most people will probably get the digital (or digital deluxe -- comes with a minion!) version.

Usually the way this works is that new areas and classes are bundled into the expansion (and as such all story/ dungeons/ etc. in those areas) while things like the level cap increase, job tweaks, and any additions in current areas are accessible with just the update that goes live at the same time.