This is why G*d invented test suites, language specifcations, and the idea of a "stable version" (all of which the Ruby people apparently haven't heard of yet).
Breaking tools due to minor upgrades, assuming they do happen (other languages' experience says that they don't, at least if you adhere to the principles mentioned in the first sentence of this contribution), is manageable. They're certainly much more benign than the security risks inherent in installing multiple competing environments for roughly the same language. Examples abound, just check the LWN archives.