Back when it originally released in 1998 for the Sega Dreamcast, Sonic Adventure was a critically-acclaimed hit, and considered by many to be the console's killer app. Then an HD port was released in 2010 that marred the platformer's reputation, with many critics stating that the game simply hadn't aged well. As it turns out, Team Sonic lead and Sonic Adventure director Takashi Iizuka agrees with that sentiment, and has a desire to remake the game to address its lingering issues.
In a recent interview, Iizuka called Sonic Adventure a "unique game," even 20 years after its initial launch. He pointed out how Sonic Adventure featured six different stories, six different gameplay styles, and the A-life Chao raising system, whereas most games don't have quite as much variety with their content. Presumably, if Iizuka were to remake Sonic Adventure, all of these features would remain intact, but perhaps some work would be done to the camera, controls, and graphics to help the game meet modern standards.
"[Sonic Adventure] was the very first 3D game that we worked on and looking at it now I can see the rough edges it has, which really makes me want to remake it again."
This is far from a confirmation that Sonic Team is actively working on a Sonic Adventure remake, and it could just be Iizuka talking about a hypothetical dream project. However, it's worth pointing out that we don't know exactly what Sonic Team is working on right now. Iizuka himself is busy producing Team Sonic Racing, but the Sonic Team studio doesn't have any currently announced projects.
The last game put out by Sonic Team was the 2017 Sonic Forces, which was met with a mixed reception from the community. The game focused on a player-created avatar character instead of Sonic himself (though Sonic still played a significant role in the game), which was a controversial decision for sure. However, it's possible Sonic Team is doubling down on the Sonic Forces concept and working on a sequel, or the studio could be working on a completely original idea for Sonic the Hedgehog instead.
However, if fans show enough interest in the hypothetical Sonic Adventure remake, perhaps Sonic Team will give the project serious consideration. And if it materializes and does well, perhaps Sonic Adventure 2, arguably the more popular of the two Sonic Adventure games, will also get the remake treatment.
Sonic Adventure is out now for Dreamcast, GameCube, PC, PS3, and Xbox 360.