Drupal 8 has now been out for six months or so. Adoption looks to be faster than that of Drupal 7 was in it's time. But between January 2011 a lot of water has passed under the bridge. The world of web development is continually changing, but while Drupal 8 has done significant improvements it's still playing with the same hand as Drupal 7 did. Not only technology wise with old (but reliable) MySQL, PHP, jQuery, etc, but conceptually it's a somewhat of a relic.
In early 2014 there was an interesting article on how to build high performance with PHP applications with ReactPHP. The original article discusses using the Full Stack Symfony Framework. Drupal 8 is built upon the Symfony HttpKernel component and other bits and pieces from that very same team.
Drupal 8 is launching soon and so is PHP 7. It's worth noting that Drupal 8 does not officially support PHP 7 at launch date, so even if you were craving for the performance boost - it's better to wait until everything in Drupal 8 is tested and proved to be PHP 7 compatible.
For PHP 7 support in Drupal 7, the plan is to backport the compatibility at a later date, as the ticket is labeled as "needs backport to D7".
You can follow the progress of the Drupal 8 compatibility work over on the Drupal issue queue:
Around the time of the release of Drupal 8 there is a more significant, but subtle evolution taking over the web. This is HTTP/2, a new and improved version of the venerable protocol powering not only web sites and applications but a lot of infrastructure messaging for energy, industry and more.
The next big version of Drupal is launching on November 19th 2015. This also means that the end of line for Drupal 6 is set to February 24th 2015. After that date it will not receive any updates. Unlike some Linux distributions, like Redhat the system does not have a third party backer to backport fixes from Drupal 7 or 8 to version 6.
Drupal 8 is set to be released on November 19th 2015. It brings improvements to many aspects of the popular CMS, but the most significant ones remain hidden from user.
One of the core components that Drupal 8 adopted from the Symfony Project is the HttpKernel. This handled all incoming and outgoing HTTP traffic. In addition to the convenience and clarity, it also handles requests independently from each other.
Drupal 8 is a big change to the popular CMS. If you plan to get started with Drupal 8 development, you should understand that under the hood it's a very different beast from Drupal 6 and 7, versions that are still in use commonly.
Every technical article you read on previous versions needs to be read with a grain of salt. Luckily the basic concepts of the system (view, content types, modules and more) remain the same, so if you're just getting started with Drupal you're in luck. You're on the same starting point with many more experienced Drupal developer.