I've got this feeling they will probably charge extra for the PhysX enabled cards and even so any game that requires a physics enabled card is going to probably lose a lot of sales.
That is a silly attitude to take. Graphics technology moves forward. People aren't going to have the same cards forever. They have to introduce the engine AT SOME POINT in order to get the user base out there to be large enough to start using it regularly, just as they did with pixel shaders.
And I'm sure developers aren't going to make games which only run with a PhysX card for another 2-3 years at least.