[millennia]

Rails does this already -

bundle update (if gem version is set with ~>)

You could easily automate this (cap,puppet,chef) if you have a lot of installs. If you genuinely don't want to test updates, you could run it on a schedule.

What it doesn't do, and can't do, is guarantee that security updates will never break your app, but they do quite a good job of isolating them, you do have to do some testing. There is possibly an argument for lts releases which receive few new features and focus on bugs, but what you're complaining about here are really the complexities of running multiple web apps/servers, not something a framework can really help with.

I don't think you have to worry about this update if you have already updated tho latest anyway (which you should have done if on 3.2.x).