It’s a collaborated effort between multiple companies. It’d be different if Harmonix was the sole contributer to the game. Now you have RedOctane, Activision, and Neversoft instead of RedOctane, Activision, and Harmonix. Not that big of a difference. And so far, the only difference visibly is the HUD and graphics. Same mechanics, same game.
This isn’t going to be a repeat of the Twisted Metal/989 Studios transition.