In no way will this harm Disney in any way, shape or form. Disney's product has been around for so long, and has had the chance to build such a niche in the market that the only thing that can harm them is themselves and overdevelopment. Harry Potter, (and yes I am a huge HP fan) when it comes to being a theme park has such a limited concept, thus a limited marketing appeal. Universal is on the right track to being true direct competition to Disney, but it is still a long way off.
"Do Not Go To Disney World With A Bottle Of Pepsi. We will never see you again, and I'm pretty sure that's a bad thing"