With most people under 30 radio in any form is becoming irrelevant. I look no further than my own children, as well as my nieces and nephews. My oldest son is 13, he doesn't even own or want a radio. My oldest niece is now 20 and her sisters are in their mid teens. They only rarely listen to the radio, preferring their iPods. Before the internet I used to listen to much more radio than I do now, even listening to shortwave broadcasts. I am a Sirius subscriber and enjoy many of their channels, but when we are driving together as a family my kids prefer to play video games or watch DVDs.
My short answer is yes, satellite radio will be around in five years time in some form. You can still buy an old-school turntable at Best Buy for your LPs too.
Long answer - the incumbent providers will not be happy with the demographics. Perhaps a satellite-based or WiMAX-based service that is not real-time, sending rich content to a mobile device at a slower rate might be better suited for a younger audience. The content could be music, games, video, books; whatever the user wanted or the player supported. It could be something similar to the Netflix model, with a user specifying content preferences on a web site, then the content spooling out to the device sometime within the next 24 hours, never needing to be physically connected to a PC. Of course you could still instantly get content on the device through synching if you chose to do so. Content should be shareable between devices as well, sort of like what the Zune is doing now. All this could be done using technology available today, using broadcast bandwidth available today. Something like this could definately be the future of radio.