I think this paragraph should be extended a little bit to mention major versions (3.x, 4.x) and the fact that these versions might break BC (mentioning semantic versioning and linking to the spec might help as well).

We should probably also make it clear that breaking BC is not the end of the world. A lot of developers associate breaking BC as what happened in the past with Symfony 1/2 or ZF 1/2 BC breaks. We should say that breaking BC can lead to simple and fast upgrade as well. I suppose that we need to define a BC break here.