Indeed.com shows no such drop in Rails job offers. Both Rails and Django are showing growth in the percentage of job offers: http://www.indeed.com/jobtrends?q=rails,+django&l=
If you fall back to a language-only search, then Python shows a bigger slice of the pie, but the original question was about web frameworks. http://www.indeed.com/jobtrends?q=python,+ruby&l=