I enjoyed Ruby as a language quite a bit. Having experienced some of Rails' scaling issues, I doubt I'd personally pick it for my next startup. I know time to market is vastly more important than scale, but it's also not hard to pick a different tech that DOES scale easier.
So, yes, there will be plenty of Rails projects to work on for the foreseeable future. The only concern I'd have is if you're being asked to work on a very old code base. That can get really hairy, really quickly. But that's the case with any language/stack.