I disagree that scalability has nothing to do with choice of framework. It happens that none of these frameworks address common scaling issues to a great extent, but that doesn't mean a framework could not do so.
Regarding the "RoR clones" claim, citation, please. Django was publicly released very shortly after RoR, having been developed privately for a couple years. I don't know about CakePHP.
Regarding the "RoR clones" claim, citation, please. Django was publicly released very shortly after RoR, having been developed privately for a couple years. I don't know about CakePHP.