Though the documentation isn't necessary for rails to run; I have found that it is most likely not stuck.
It took a little over five minutes to complete gem install rails -v 4.1.0
on my quad-core i7, but your experience might be worse if you have a slower computer (it took 15m 47s for just ri and an additional 16m 21s for RDoc on my 4 logical core i5). For those who want to make use of the ri and RDocs you will merely have to wait. For those who have no intent to ever use them you can execute
gem install rails -v 4.1.0 --no-ri --no-rdoc
This took ~30s on my i5 machine.