It will remain perfectly viable until the software on it becomes obsolete. When the browser(s) cannot render the latest pages, plugins such as flash cannot be worked around or everyone converts their music to MP5 which no-one writes a decoder for, then it becomes less than useful.
Until that day comes, it does everything I need it to do and I will continue to use it and respect it.

There will have to be a LOT of research done for it's replacement, that's for sure.