I think it needs more work. While it is obvious what it's based on, I think it doesn't quite fit in with TF2 style of hats. As in, it's more of some sort of indistinguishable shape than to be properly identified as a hat. Plus, perhaps can bare more resemblence to Sonic's head than just the quills alone?

For example, what if it included green-tinted wind-protective goggles? You can get goggles that have single frame but still padded around the eyes. If you go for the Aviator Hat and Goggles approach (without ripping off the Barnstormer) it could be more identifiable as a hat. The plush like material could also be replaced with the kind of leather used in aviators hats to make it look more natual.
There could be more material around the goggles as well to bare more resemblence to Sonic's brow. And to bare less resemblence to the Barnstormer, have the chin strap buckled up.

With Sonic Mania and Sonic Forces upcoming, I'm hoping Sega and TF2 will consider accepting cosmetics for it, because a Sonic hat would be pretty cool. Sega has granted promotional items to TF2 in the past (Alien, Spiral Knight, The Cave, Football Manager and various Total War promos) so there might be a chance for Sonic cosmetics in TF2.
(If Mario's hat can make it into TF2, why not something of Sonic?)