When has MS ever encoraged multiple vendors in a market niche that it occupies? If MS brigs out a MP3 player, I would expect them to attempt to tightly tie it to Vista, to have a unique format that plays "best" on MS's player, etc. That's they way they've always operated. Look at OS/2 and DesqView and GEM and ....
As for what Zune is or will be, I think it's best to wait and see. Why feed MS's spin when it may not have decided itself what it's to be or which companies it wants to crush first?