Linux will always have a place, but the likelihood of it ever
being a simple "install disc, click file, application easily works" is highly unlikely. (compared to Windows/MAC anyway
Until such, it will never be considered a 'true desktop' replacement. Distros like ubuntu and Opensuse et al are making great progress, but are still far behind the curve. And that curve is forever widening.
As much as I like some distros, I always end up primarily using Windows. Some of that is based on familiarity, application compatibility or an overall lack of patience with counterintuitive behavior that is inherent with linux distros.
As it stands now, and for the foreseeable future, Linux will remain a 'niche' sector in desktop computing.