There is an opinion piece at http://blogs.zdnet.com/BTL/?p=2987&tag=nl.e622 that suggests with the DRM and patents that Apple controls it may some day become a monoply that controls digital media and phones. I am not an expert in this area and since I have (thus far) resisted the urge to buy an iPod I am not sure how much this will affect me but it is an interesting scenario.
I can certainly see some competition for Apple. If another on-line music site (say MSN music or Wal-Mart or whomever) were to gain popularity it could certainly put a damper on the "planned" take over. Also if the RIAA decided that they would like to do the bullying rather than be bullied they could look for an alternative DRM provider. It would cut sales immediately but could force Apple to adopt that DRM technology for the iPod to continue selling.
In any case I think the competition leading up to whatever happens will be interesting and could be very good for us all.