I don't agree. I think that Apple will not sell additional bands to customers on launch to maximise the band options for customers who want to buy an Apple Watch.
It would not be good if you go into an Apple Store and can't buy the watch you want because they have run out of the band you want. In order to reduce the likelihood of this on day 1, I would think they are going to limit your purchase to 1 band only. After the launch period and they have satisfied initial demand for the Apple Watch, you can then purchase any band you want.