Quick fact checking:

Job offers on Dice.com:

Java: 16837

Javascript: 10161

C#: 8011

Ruby: 1707

Ruby on Rails: 679

Scala: 82

Market share on Tiobe:

Java (#1): 18.5%

C (#2): 16.27%

Ruby (#11): 1.48%

Scala: not in the top 20

So, the article is right: Ruby on Rails is still quite niche.

(can't believe HN won't let me format this comment better than that)