I don't think a straight comparison with Wordpress is useful. The two work differently and perform different jobs.
My reading of the article is that if you want to generate content from a single source, using a simple markup language, and are reasonalby technically savvy, then Jekyll is more likely to fit the bill. Especially when you want to generate the code locally and then post it up to a public site. Also if you want to make the public site truely static, then Jekyll is the solution.
If you need universal access from any or many locations by one or more users who may not be technically minded, then Wordpress is the better solution.
I think Jekyll looks really good. Definitely another useful addition to the web toolbox. But just as I didn't chuck out all my screwdrivers when I bought my first chisel, I won't be migrating my WordPress sites to Jekyll now that I've found it. However, there are a couple of fairly static sites that I have that could be much more easily managed via Jekyll.
Reggie's right, perhaps the comparison isn't particularly helpful.
From a development POV there's not much difference: If you develop a WP theme you'll need to install some form of AMP and set-up a db, which you don't with Jekyll. You'll also need to learn the various functions, the loop concept, functions.php etc., In comparison, Liquid doesn't look particularly complicated.
Of course, you lose comments (which you could offload to Disqus or Intense Debate) and plugins...