The first trailer forand the reaction was... mixed.
Mixed? That might be underselling it. Try "deranged", "insane", "tinged with hysteria". Some people were mad that it wasn't the Sonic they remembered. Others were angry he had large, well-defined calfs. Mostly people were freaked out about his teeth.
Regardless, the reaction wasn't positive.
Director Jeff Fowler has heard the criticism and now, pretty late in the game, he's promised changes.
What will those changes be? Tough to tell. Some artists have come up with their own designs, but the truth is we have no idea at this point.
It all seems extremely last minute, and many have commented that making core changes to your main character, when the movie is due in November is going to put a lot of pressure on the folks working on the movie's CGI.
Fans have been criticising the Sonic design since the original poster, so it seems strange that they've waited until now to make changes. Also worthy of note: Adult human beings losing their mind on social media because the design of the main character in a movie aimed at children doesn't meet their nostalgic needs. Completely normal and not strange at all.