There's room for an extensible blog platform like WordPress but with well defined performance safeguards for plugins and themes. WP users never rate plugins or themes based on performance because performance degradation due to plugins or themes is rarely visible to the end user. So they're almost always rated based on functionality.

So if you could somehow build performance-safe extensibility, you could emerge as a solid alternative especially if you continue targeting developers (they spread the word more effeciently.

Anyway, perhaps I'm biased w.r.t performance because I built Cachoid (for WordPress, Drupal, Joomla, etc) but this could be a niche with interesting growth.