It was confirmed last week that the plan for Sonic Frontiers was to be released on the franchise's 30th Anniversary, but plans changed. During an investor Q&A at the end of 2021, SEGA higher-ups basically confirmed that rather than try to push their latest Sonic The Hedgehog game out onto the masses just to meet an anniversary, they chose to withhold the game to make sure it was of quality and not a buggy mess for the sake of a celebration. Here's a couple of selections from the meeting's notes.
Originally it was planned to be released on this year, the 30th anniversary of Sonic, but we have postponed the release for a year in order to further brush up the quality. Not only for this title, but during the development phase, we have been steadily conducting analysis to improve the quality of the title before release, such as introducing game testing based on external evaluations, and I have a feeling that it will become a good game and have high expectations for it. […]
For the pricing strategy, we feel that we are at a point where we need to rethink. For example, for the new Sonic game, as we are focusing on quality and spending certain amount of money on development, we think it is important to maintain the price by maintaining the value of the IP at high level, rather than simply lowering the price at early stage to increase the number of unit sales.
As to when we'll actually see Sonic Frontiers, that's an entirely different discussion as it would seem the game was near enough to the end of production to have the conversation. But considering the announcement trailer came during The Game Awards 2021, and they have said it won't be released until the 2022 holidays on their website, the likelihood of getting this earlier that that is pretty slim.