The rationalisation seems pretty clear to me. The current situation, where each release significant changes only the 3rd level (below-minor) version is silly. (As jku points out, you get a situation where 2.6.0 and 2.6.39 are vastly different, with no change to even the minor version). The obvious remedy is to switch to incrementing the minor version with each release.
The move to 3.0, in this picture, is just a way of doing this from a clean slate. The alternative, going 2.7, 2.8, 2.9.. is less inelegant -- apart from anything else, the 2.x series is bound up with assumptions about 2.odd being development-only.