Today I went to the mall and exchanged my black leather loop for blue and walking back, as I walked by the Brighton store, had the thought that the next "evolution" of 3rd party bands will come from designers/designer stores. Stores like Brighton, Express, Michael Kors and possibly even like American Eagle, etc.
These will likely be made for them by an established company (like Fossil makes a lot of designer watches like Michael Kors). But they will be fashionable and have good warranties, etc.
There are well respected watch band/accessories stores and sites already out there. They make excellent bands that are currently used on high end watches. These are beautiful and functional bands like leather, skins (lizard, etc), rubber (dive watches), nylon (NATO straps) and quality metal/link bands (most well under the cost, while better quality than current Apple band offerings). I can't imagine it will be long before they offer at least their most popular bands with "Apple Watch adapters".
There have already been reports of designer watch sales from Michael Kors (and others) being down. My bet on these fashion brands that watches don' make a majority of their sales (but are significant and help the brand) will just also jump on the Apple Watch band, band wagon (pun intended).
I think the more interesting prospect will be how soon true watch makers offer accessories/bands for Apple Watch. For example, can you just imagine some of the Tag Heuer bands being available for Apple Watch? They are all so damn awesome,
http://us.tagheuer.com/en/tag-heuer-carrera/tag-heuer-carrera-models