Here's the real issue. WordPress is more than a blog. Ghost is only attacking the blogging aspect of WordPress. The rich themes and plugins ecosystem of WordPress cannot be matched no matter WHAT anyone thinks. Because of this, WordPress is widely used to develop all kinds of sites.

Hell there's a company in my area (sadly I worked there years ago) who literally manages 200+ local businesses sites and they're all powered by WordPress. I'd say 1 or 2 of them are actually blog having sites. The rest are just "I want to be able to edit this section of content myself" sites.

WordPress makes it insanely easy to build a site for a client or even anyone who's vaguely familiar with web development.

Go get a cheap shared hosting account, click that 1 click WP install button, login to your new site, search for a theme you like, install it in a click, make a few minor tweaks, find some plugins that do stuff you like, install them in a click. Done.

Until people realize this, there's no "taking on WordPress".