Will my contrib modules keep me stuck in 5 forever?

Then you may either be stuck for now or have to look for alternative modules.

Some modules you are using may never get ported, and this is a fairly common occurrence when upgrading to a new version of Drupal, so I would start looking for alternatives.

ZivTech: Illuminating Technology
Future Majority: Blogging Progressive Youth Politics

You could also ask the providers if they plan to upgrade their modules to D6

What can be wrong with being stuck with an older Drupal version is that after 2 major new versions your version will be unsupported, at least officially.

This means that there won't be any more security updates, compatibility updates for new PHP versions and similar things. But there may be independent support sites for old versions.

What you can do to minimize inconvenience is to (a) stick with active popular modules which will certainly have an upgrade path and (b) stir interest and help out in any way you can with the other ones, for reviving them or for methods of migration to new ones.

1. First option you can help with Drupal 6 modules testing. Some modules are available on Drupal 6 but not release yet because they need to be tested first. Anybody can test modules you don't need to be a programmer. How to test modules: http://drupal.org/contribute/testing
2. Second option if you're a programmer you can contact the module maintainer and offer to help with the port to Drupal 6. How to help with development: http://drupal.org/contribute/development
3. Third option you can pay a programmer to port the module to Drupal 6 for you.
   • Search the Drupal paid services directory: http://drupal.org/paid-services
     
     or
   • Post a free ad to find a programmer: http://groups.drupal.org/jobs

Hope this help,