Drupal 7 is a powerful, robust tool, that allows your site to grow in almost any way imaginable. But with this flexibility comes a steep learning curve. Drupal 7 has a reputation for being hard to use, harder to learn, slow, and only easy to develop if you already know what you're doing.
Drupal 8 is going enterprize. It will probably be easier to use, but still harder to learn. It will be slower to run than Drupal 7 (unless you have a beefy hosting environment). The code in D8 is very different from D7. Developers for D8 are going to be more expensive, harder to find, and development time is going to be longer (at least initially) as everyone learns the new systems.
Small to medium-sized businesses are already feeling the increasing development (and hosting) costs that are associated with running Drupal websites. How much of the Drupal ecosystem is made up of these sites, people, and developers? How will they fare in a Drupal 8 world? How does that affect the entire Drupal ecosystem?
I'd like to offer an alternative: Backdrop CMS.
Backdrop CMS is a fork of Drupal. It splits from Drupal 8 very early in the development cycle, before the introduction of the Symfony framework. It's code is similar to that of Drupal 7 but also includes features comparable to those in Drupal 8.
The primary goal of the Backdrop project is to decrease the barrier to entry. This includes lowering the system requirements (meaning more affordable hosting) as well as making the interface easier to use, and the code easier to learn.
Come hear more about Backdrop CMS.