Well, that is a bit of a loaded question. It seems you feel that a community run distributions somehow warrants concern for their future, or you feel the opposite and question whether you should have concern for commercial distributions' future?
Neither I'd say. Debian is one of the oldest community run distributions, and has over a thousand active volunteer developers. It's not going anywhere but forward, and the Linux Mint Debian Edition is based on it. Ubuntu, as a commercial distribution (Canonical is intending to make a profit), has grown to just over five hundred paid developers is continuing to make inroads into having Ubuntu preloaded on hardware. Despite how some people seem to enjoy criticizing Ubuntu, it doesn't seem to be going anywhere but forward either, and the Linux Mint Main Edition is based on it.
There are plenty of other examples of community and commercial distributions that have a long track record and for which I wouldn't be much concerned about their future (Red Hat, Fedora, Slackware, Gentoo, Arch, etc.). The GNU/Linux Distribution Timeline can be fun to have a look at, to trace the history: http://futurist.se/gldt/
But I agree with Orbmiser, the desktop environment and other applications are what you actually use from day to day. If you are using KDE for example, you can also hop on over to a BSD should Linux go away completely. Finding a distribution with a community that you feel at home in is I think most relevant. Nobody can say what will happen with a distribution in 3-5 years, so focus on the "now" and use something that you feel at home with and helps you today