We're well into 2015 and it seems that at the PHP 7 crew is holding on to their promise of releasing PHP on time this year. A few days back the PHP team tagged Release Candidate 1 for PHP 7 for release. This is a first sign of an actual release, since there is nothing stopping the PHP 7.0.0 RC1 being the release that actually ships. Probably it won't. but it's looking very good.
In the meanwhile Drupal 8 is release is inching towards a release, with only eleven critical issues at the time of writing. Drupal 8 is yet to reach the level of an RC, but given the investment Aquia and other companies bet big on it. The Drupal community must release a final version of Drupal 8 in 2015 or coinciding with a January launch of Drupal 7. Infact, Aquia already offers Drupal 8 on the Aqcuia Platform for testing.
So both PHP 7 and Drupal 8 are on track for a launch in 2015. But what I am already looking for is Drupal 9. This release will be more of an evolution rather than the revolution the Drupal community faced with Drupal 8. After the rather painful release effort over the years, I think everyone will want less backwards compatibility breaks and a shorter development lifecycle.
With PHP 7 being the largest release of PHP since 5.0 it'll bringing some new features to the language itself. Drupal has now adapted Symfony Components, but it is by no means limited to those. As we move towards Semantic Versioning in Drupal 8, we can expect a clearer policy on updates and their backwards compatibility.
With modern PHP methodologies, Drupal 8 can already start evolving in smaller steps by replacing individual components by using interfaces. While this does not turn Drupal into a complete CMS similar to WordPress with short release cycles, it does move it from the radical big bang releases every four-five years. Performance of Drupal 8 will continue to evolve and so on, without large fanfare.
To be I'm not sure there will ever be a Drupal 9. With Facebook, Windows and other platforms inching towards a continuously evolving product in marketing terms. Sure, Facebook's tech stack with HHVM, React, Flux, etc. will have version numbers and releases. But only people who need to know about the versioning know about it. WordPress is already pretty much there. We need to follow.
So just as Windows 10 might be the last Windows - so might Drupal 8. It'll just be Drupal, which is always changes.