Final Fantasy XV

FF8 was neither renaissance nor steampunk. It was set in a modern era but also included an isolated, futuristic area. FF6 was totally steampunk. FF7 was a mesh of steampunk and modern era. Modern era doesn't necessarily mean a world filled with metropolitan and technologic cities.

My biggest sadness about modern FF is the absence of a class system, or at the very least having each character with a defined class(like 4 or 9). But that's just a personal preference.

Having the lore and themes of Final Fantasy being so flexible can be powerful, or to some fans it can be a weakness because they see some of their favorite themes (like the crystal) become so forgotten.

The theme of the crystals are still there it's just not as blunt as a giant crystal. In X the faith were the crystals, in XII the sun cryst and the nethicite cut from it and so on.

Edit: it could be argued that the concept even carried into Kingdom Hearts in that the princesses of heart could be compared to the crystals.

The team found it difficult to fit Stella in Final Fantasy XV, so she won’t be included in the game. They instead created a new heroine, Luna, who has a different role in the game. We’ll hear more about her in the future.
The sequence in Final Fantasy Versus XIII in which the capital city of Insomnia is attacked by enemy troops after the party in the castle. That scene is no more part of the game. In Final Fantasy XV Noctis and his friends leave Insomnia before the attack.
There will still be gameplay set in Insomnia, but it won’t be around the same time line. Tabata-san promised that they will be great, and encouraged fans to look forward to them.
The black-haired woman and the female dragoon showcased in previous reveals are still in the game and have an important role in the story.

Well, at least we know FFXV has a strong crystal theme, now how strong the story revolves around the crystal we'll just have to see! :)

Anyhow it's about the tone and feeling. Fanbois are gonna defend their team to the death no matter what and it's pretty easy to spot the "hero must ride a motorcycle and have emotionally misunderstood issues" types.

Crystals in IX were the 4 artifacts used to summon alexander i.e. Desert Ruby, Hawk Fang, etc.

Square Enix has confirmed that it’s in talks with Avalanche Studios to use Just Cause 3 tech in Final Fantasy XV.

In an interview with IGN at Gamescom, Final Fantasy XV director Hajime Tabata revealed that conversations have begun about a collaboration between both studios’ development teams.

“We’re talking to their central technology team based in Stockholm in Sweden about a certain collaboration we might do with them and the Final Fantasy XV team,” Tabata told IGN via a translator.

“We’ve got really great hopes for this discussion. What we’re going to be talking about is possibly being able to use their really unique, really high level amazing technology they have in their studio and using it as an add-on to enhance the quality of a certain specific part of our Final Fantasy XV game,” he explained. “We really think something very special may be coming out of that.”

Tabata cautioned that these conversations have only just begun, so there’s no guarantee that there will be any results just yet. When asked exactly what this collaboration might entail, Tabata explained that Square Enix is especially interested in Just Cause 3’s verticality.

“When I saw what the guys at Avalanche Studios were doing with Just Cause 3, what really impressed me was how they have that vertical element to their games and the technology they use to achieve that kind of thing,” he said. “So I really felt that if we could borrow some of their technology and have some help on what they do to achieve that and put that into our Final Fantasy XV engine, we could see a lot of really great breakthroughs in what we’d be able to do with the game.”

Tabata feels that a partnership could be mutual, as Square Enix has “very great technology within our department, within our team, aimed at creating real-time footage as you saw in the footage shown in the trailer today. So maybe that could be a great help to them as well.”