The next SoulCalibur titles may be remasters of older entries, according to a statement from industry insider Nick Baker on the most recent episode of the Xbox Era podcast.
At around the two-hour nine-minute mark of the podcast, Nick states that a trusted source informed him that Bandai Namco, the developer and publisher of the SoulCalibur franchise, is potentially cooking up remasters of the earlier entries. Nick is quick to note that he's uncertain whether this would just be a remaster of the original entry, or some kind of collection.
He also goes into some slight speculation, but makes it clear that he doesn't have any specifics beyond there potentially being some kind of remaster in the works, although he also notes that there may be some kind of Game Pass deal in the works too, presumably alluding to a day one release on the service.
Nick notably has quite an accurate track record regarding leaks, including the likes of PlayStation Plus titles prior to official announcements, although given the nature of rumors, this could go either way.
In the franchise's history, the only game to receive an HD update has been SoulCalibur II, via an HD version downloadable on PlayStation 3 and Xbox 360 all the way back in 2013, while the first game got a no-frills port to Xbox 360 even further back in 2008. Meanwhile, III, IV, and V are all stuck on their original hardware, with the 360 versions of IV and V not even being included as part of the Xbox backwards compatibility program.
What makes remasters of the games past the first entry especially interesting is their inclusion of guest characters as well as console-exclusive characters. The Legend of Zelda's main protagonist Link was famously exclusive to the GameCube version of II, while the Xbox and PlayStation 2 versions got the comic book character Spawn and Tekken icon Heihachi respectively.
IV took things a step further with the likes of Yoda, Darth Vader, and Starkiller from Star Wars being included as playable guest characters, while V had Assassin's Creed's Ezio joining the roster. Depending on Bandai Namco's intent regarding the remasters, they may be hesitant to go through the trouble of re-negotiating some of these characters.