This isn't likely. I'm sure the high end bands will be exclusive to the high end watches. Apple doesn't want people buying the cheap sport and putting a high end band on it, and they certainly don't want to see mismatched watch/band combinations in public tarnishing their design "excellence".
I disagree. Wholeheartedly.
I believe that consumers will have the ability to buy any and all bands WITHOUT buying all 3 watches. In my opinion, that's like saying: "Apple would never let you buy an orange case & a blue iPhone 5C at the same time from the Apple store. Those colors don't go together!" Apple is NOT in the "making accessory choices for you" business. They are in the "sell you as much as they can business". I have little doubt that Apple would jump for joy if people started collecting all six bands... and wouldn't give a fig if they looked arbitrarily good to them or not! They'd be chuckling their way to the bank.