From what I've seen, the Eggman support thread has jumped up hugely in numbers since Sephiroth's reveal. He's also at the top of the Global Smash Roster when it comes to Sonic characters. While I definitely know there's arguing of whether it should be Tails or Eggman, or even Knuckles or Shadow possibly (I want them but I can't deny being an AT hurts their chances), I don't think it's to the point where we're cannibalizing each other in a situation where no one wins. Because even then, we're still making our voices heard, so there's undoubtedly a lot of fan demand for a 2nd Sonic character.I just had a thought: everyone here agrees that we need a Sonic character. But... could that be our greatest weakness?
Very unified character fandoms such as Bandana Waddle Dee, Geno, or even Rex can band together and focus on requesting that character. Other than the nebulous idea of having a Sonic character, Sonic fans can't exactly agree on what Sonic character that is (Sonic fans not agreeing on anything, like that's new). The individual fandoms of each Sonic character could be cannibalizing one another, creating a situation where no one wins.
Also, take a look at the fanbases of ARMS and Final Fantasy. I'm sure there was a lot of debating and disagreeing in those fanbases over which character should get in next (I was a Mechanica/Noctis man myself), they still got a character in Smash, so I don't see why the same can't happen for a Sonic character.