It's out now
Support for Drupal 6 by the core and security teams will cease - that means no security fixes, bug fixes or other core updates.
Stable and mature
Nearly all of the functionality you have on your Drupal 6 site can be implemented using contributed modules. Anything else can be developed bespoke for your website, following best practices.
Near "end of life"
Soon Drupal 6 will no longer be supported. Not upgrading can leave your website vulnerable. We can help you upgrade your Drupal 6 site to Drupal 7 now.