Earlier this year, Sonic team lead Takashi Iizuka hinted that Sega might be thinking about a return to the Sonic Adventure series, implying Sonic Adventure 3 might be in development. He was forced to walk back that rumor in June and by July he was wistfully yearning to return to Sonic Adventure "someday." That day might be closer than Iizuka let on. A prodigious Sonic Adventure modder has found evidence in Sonic Frontiers that Sega could be remastering Sonic Adventure and Sonic Adventure DX for a potential future release.Note there are some slight Sonic Frontiers spoilers for the third island. Fair warning.
SPEEPSHighway, a known Sonic Adventure modder, recently got a hold of the Tails flashback cutscene from Sonic Frontiers and performed some forensic analysis of several still images. They note that the flashback scene seems almost like an exact replica of same scene from Sonic Adventure and Sonic Adventure DX, with the Sonic Frontiers flashback suggested to be an edited amalgamation of the two.
In several posts, SPEEPSHighway notes how parts of the flashback appear to be from Sonic Adventure DX, such as the Twinkle Park Path and parts of the missile, but other parts are from the original Dreamcast version. Overall, the lighting appears to be from the DX version, which was a port of the original Sonic Adventure with some updated graphics, but some objects and models are from the Dreamcast game.
As suggested by several Reddit users, this could be evidence that Sonic Adventure is already being remastered and could be released for the game's 25th anniversary. That'd fit the mold set by Sonic Origins, which re-released updated versions of the first five Sonic games for Genesis and Sega CD.
Can't wait for a Sonic Adventure remaster? There's a mod for Sonic Frontiers that'll give you the stubby Sonic Adventure version of Sonic, which is basically halfway to a remaster.