Drupal Geeks are experts in content migration and, CMS upgrade for complex sites. From time to time, Drupal will release minor updates, or patches, primarily for security.
When a committed Drupal support team works with that as the cornerstone, the project is well on its way to success.
The good news is that Drupal 6 can be made to work with PHP 5.6, which is actively supported.
Drupal 6 core needs just a few patches but many contributed modules will need to be updated and/or patched. To find out, you first want to get a list of what errors your site is producing now.
Drupal 8 core was built with the plugin-based architecture, which allows importing of data from any external data source, even when using your own custom plugin.
Drupal 8 migration will include content import core modules to enable you to import content from Drupal 6 or Drupal 7 sites.