They only used Unreal for one title. RGG said they are committing to their proprietary tech earlier this year. I'm pretty sure the new VF is using Dragon Engine too. Visually it looks like their new games could be dropping PS4/Xone support and and the visual base will be current-gen consoles. Both VF6 and Century are in early stages of development and won't release for a while. For games outside of RGG/AM2 studio like Jet Set Radio, Sega is using Unreal.
RGG said they have their studio learn Unreal and Unity to see where their engine deficiency lies, and that helps them upgrade Dragon Engine.
今や世界中にファンを持つ、セガの人気タイトル『龍が如く』シリーズ。初代の作品から同シリーズのバトルシステム開発に携わり続け、現在「龍が如くスタジオ」の技術責任者を務める伊東豊さんにインタビューを実施。「龍が如くスタジオ」のプログラムチームの軌跡に迫った。
type.jp
- With the future of the series in mind, you're training new recruits to give them a wide range of experience.
Yes. However, the Dragon Engine is something we absolutely cannot do without when making Yakuza , and we will continue to develop our own engine.
Dragon Engine focuses development resources on the features necessary for "Ryu ga Gotoku," and the biggest advantage is that new features can be added quickly. If you use a general-purpose engine, you can send an email to support and get a response in about three days, but if you ask the programmer next to you, it only takes five seconds. I think this difference is big.
But that doesn't mean we should just think, "Our game engine is the best!" I think that we programmers, in particular, should always have a sense of crisis and think, " They're better than us, we have to work harder."