There will be new features to make character customization more fun
There will be a new mode that makes use of the Switch's Joy-Cons, but the defails are unknown (this will be demonstrated in Magical Mirai)
There will be 300+ modules, including one for the theme song
A paid DLC set will be available for PS4 Future Tone / FT DX including the new songs, also in early 2020
The followings are from the interview:
They've been asked to make a Switch version since a long time ago, but solidifying plans to make a new game took time
PS4 Future Tone was more well-received than expected, so they thought they'd return the fans' thanks with a new game
Switch is a suitable platform in the sense that the series originated on a handheld
The songs are chosen on the criteria of being representative of the various eras of Hatsune Miku, and being fun to play with Joy-Cons
They did want to include all songs, but the limited ROM size and the development time needed made it a difficult goal
The theme song itself is a secret; its themes are "the past 10 years" and "the future 10 years"
Joy-Con/EASY is adjusted to be easily playable even by kindergarteners, but HARD should satisfy rhythm game fans
I've seen quite a lot of speculations on what the Switch-exclusive mode would be, from touch mode to mirai-style charts to a dance mode. It turns out to be a Joy-Con mode… interesting.
Future Tone currently has 399 modules! It should break the 400 barrier after the DLC. And I wonder if they're finally going to include Hatsune Miku V4X in both versions. Come on! Crypton's own polls show that people like the V4X design better than V3, Append and original!
I thought of a lot of reasons both for and against a Switch version of Project DIVA. The main reasons for it are the versatility of the system, the disjointed directional buttons, and there's a sizable fanbase on the Nintendo side. Reasons against are also the versatility (which makes testing difficult), the less durable and asymmetrical controller, and that the gameplay itself screams PlayStation. Kudos to the team for making the move anyway.
And just as I thought, game size was one reason we only get 101 songs. I never expected a full Future Tone port anyway. But I also didn't expect to see Future Tone's game system used without changes, multi-press and all.
The comment on the difficulty worries me a bit. I hope they aren't going to stop at HARD. That would lead to the same problem the mirai series had: being too easy for rhythm game veterans. I hope all the original difficulties get carried over, even if most players can't handle it. The existing screenshots are already suggesting that the Switch/PS4 charts will be identical, so this shouldn't be so unreasonable to hope for.
And one last thing, I hope the icons can be changed. I use arrows in both mirai DX and Future Tone DX, eliminating the whole X/× button issue. The team does realise that Project DIVA has quite a lot of cross-platform players, right?