[dragonwriter]

It's worth noting that Rails has adapted to compete with alternative Ruby frameworks that arose to deal with Rails issues (both general and specific use cases), and has merged with one of the alternatives. Insofar as either Ruby the language or the main Ruby implementation are issues holding Rails back, both have evolved considerably and continue to, and several alternative implementations capable of hosting Rails have developed.

Rails has quite a bit of life left. Sure, with more choices of frameworks available, there'll be fewer cases where it's the only viable choice for a project, but it will be competitive for some time.