In software development, there usually comes a point where you stop working on features that are draining resources, and focus on getting the features that can be finished on time done.
However, I don't see this happening in linux, as there will always be someone using a software project, linux distribution, or project fork that will disagree with the decision to cut it. As the leading figures tend to listen to these users more frequently than not, there is a great deal of effort spent on them that could be better spent on a different area of linux.
Since there is no real one true leader (some would say Linus Torvald, but he really makes strong suggestions, not commmands or decrees) there is no one to force consensus. Take a look on sourceforge for projects that have not been touched in years and you will find more than a couple. As the developers realize just how much effort is required to support different versions of linux, and adapt to changes on dependencies like glibc or gtk, they may realize that if they working this hard they might as well get paid for it. This will lead to both a decrease in the size of the linux volunteer army, and a potentially abandoned project.
The many different distros of linux are both a blessing and a curse. Projects like Slackware are not very user friendly, but still have a very passionate base. But ask yourself, would you rather have a niche distro? or a more complete installer and hardware detection scheme for a more wide-scale distro? Is there even a way to make everyone happy here?