Ok that’s all nice and well but shouldn’t they be updating to Rails-4 by now?
I think you’re missing the point. IMO the actual tech doesn’t matter.
Rather, so often, we are inclined to face these types of “big refactors” by being faster than the rest of our team, or worse, putting in a feature freeze. I think it’s encouraging to see that a relatively complex code base like githubs can be incrementally upgraded.