Sonic still sells decently these days, and that is despite Sega seemingly having no quality control/ care of keeping their IP's in high esteem. Hopefully Sega takes better care of Sonic and their other franchises going forward (doubt it).
I wouldn't be opposed to sonic in theme parks, if they did do something I think something like the image below would be kind of cool with a coaster track in the center. Would be like classic sonic.