Incredibly horrible disastrous sales crash.
The sales have completely collapsed, it sold 2.5 million in one month, we are now 4 months after that. Like most Sonic games heavily frontloaded but this one one of the biggest frontloads out there which had people wondering if it could sell 4 or 5 million or possibly be in the top 2. People who were sucked into the hype and fans have already brought the game.
End of January the series was at 2.9 million.
The game has also already been discounted multiple times. Watch PS Plus or Game Pass be the next destination in a few months. The game will end with good sales but it will almost all be because of what they did leading up to November.
The amount of discussion surrounding the game is also notably less than Forces, which did much worse by a very wide margin so that tells you that there's definitely an engagement issue here for many of the non-fan users who got the game.
However, the sales diving isn't new, that's been happening to Sonic games after the launch window for several entries now, just this one is crashing a lot harder than usual which will have an impact long term.
It is however still going to be one of the best selling games in the series and a sales success, for a Sonic game, just based on what that frontloaded November did for the game.