Going out on a limb here, but maybe they are gonna replace the class system with "Onion Knight" job, and do away with classes altogether. Onion knight is typically the thing you choose when you want to be sort of mediocre at everything, which is kind of what the class system is when you think about it. It lets you cross class a lot of skills but you're not as good as a regular job. Classes were supposed to be the thing you do when you want to solo and maybe you need some extra skills, so onion knight could be the go-to job for soloing as a jack-of-all-trades, master of none, sort of deal.
On another note, I want to concur with the person who said that ishgard looks like the mother crystal. I think the way they've depicted the city here is probably intended to invoke that image. What the city of ishgard has to do with the mothercrystal ? Who knows.
