What makes Drupal 8 so special?
- Improved mobile support: You'll notice this most on the Drupal administration pages.
- Better multi-lingual support: D7 was better than D6 at handling multiple languages, but D8 hopes to make it even easier to manage.
- Configuration Management: A better process for capturing the Drupal config.
- Accessibility / HTML5 / Twig: Overhaul of the front-end technologies to improve accessibility and the theming layer.
- More functional core: With more options for structuring data and rendering content.
- Usage of external libraries: That make Drupal even more powerful and flexible.
How long will Drupal 7 be around for?
A long time. The time gap between the release of Drupal 7 and Drupal 8 will probably end up being not far off 5 years, and if it takes a similar period between Drupal 8 and Drupal 9, then we can be assured of Drupal 7 support until at least 2020.