The reason I am convinced Drupal has staying power is the people.
I think the power of Drupal is the community.
Drupal is a great framework/CMS, but it is not the only option in this market-space. The Drupal community and project have many different entry points for becoming involved and meeting and collabortating with others. When I came to Drupal almost two years ago the entry point for me was the local Drupal User Group here in Seattle. I think our group is a great model for other groups to follow, we have a great core of committed people, we are committed to our local community and we focus on remaining a place that is available to anyone interested in Drupal, regardless of their experience level.
Committed leaders are at the core
Averaging over 20 people each month, our group has grown since the first meeting I attended where 4 of us met in a cafe. Much of the credit for our growth and staying power has been the commitment of a core of people who schedule and lead the meetings, organize and present at DrupalCamps and answer questions on our groups.drupal.org page. This is a familiar refrain for those in the open source/Drupal community- the core people are committed to the flourishing of a project and demonstrate that through hard work. These people are vital to our (your) local group's success. How can you support them? One thing is say "thanks". Another is look for ways to help, don't wait to be asked. As members of the group find value, there should be an expectation that they will become a part of the process they have benefited from. This goes for Drupal shops too. Our meeting is often a place where local shops come to find talent, so supporting the groups efforts should be a priority for these business'. When I started working with CivicActions I was pleased to learn that they put their money where their mouth is by offering a stipend each month for time spent working with your local Drupal User Group. I feel that this is a great way for companies to support and establish local user group leaders.
We are committed to our local community
In my experience, some of the coolest things about our Drupal User Group here in Seattle has been our impact regionally and locally. Our annual DrupalCamp has grown each year and been a fantastic event for all involved. People come up from Portland and down from Victoria and Vancouver B.C. to attend. Many of our members go to the DrupalCamps in those cities as well. It is fun to see the local flavor and learn with our neighboring Drupal User Groups. Recently we came together to build a Drupal site for a local arts oriented non-profit in what we have called a "barn-raising", as a service to them and a learning opportunity for SEADUG members.
We are focused on being inviting and open to all
One of the things that is easy to do once you start making your way up the Drupal learning curve it to forget what it was like when you started the climb. I am always impressed how the group leaders intentionally set our monthly agenda to be certain that the group stays a place where anyone can have a place. We have the "What is a Node?" question almost every month. While some may tire of constantly answering this question, the patient answers and dedicated time to beginner questions has been rewarded with continued growth in our group. This is especially important to me because as I began trekking in the foothills of the mountain that is the Drupal Learning Curve these folks listened to and answered my questions. Last month conversations ranged from the absolute beginner to questions about load balancing servers and stream wrappers in Drupal 7; there was space for all. This has been a mark of our group and something I would stress to anyone starting a local group, always ask yourself how you can serve the new person. As our group gets bigger I am sure we will run into some growing pains because the interests will become more varied, but I know that there will always be a commitment to remaining a place for all to come and Drupal together.
Drupal is growing. More and more large Drupal sites are being built, Drupal companies are being formed and developers are drinking the Drupal Kool-Aid. This is great, but I believe that the community must respond with growth. It is entirely possible to use and benefit from Drupal as a developer or business without the community, but once you have tapped into the community I believe real growth as a project happens. This is why I joined and support my local user group and urge you to do the same.