Just in my own experiences at work and with friends, I've found the opposite to be true - people pick up the language to use the framework and haven't met anyone that knew either language before choosing which one to use. Plus both frameworks (especially Rails) have a history of encouraging people to take that route as well.

That also partly explains why I started a Ruby tutorial ages ago and never got around to finishing the series, even though I still get pretty good googlejuice from it:

http://alabut.com/nonsense/2005/03/ruby-self-tutorial-day-1-...