There's lots of points you wing attract developers with out-dated hardware, and you are unlikely to see phones with atom chips as standard.
The whole point with win8 is to combine all the OS in to one. Wp8.1 and w8.11 take this a step further making it one store rather than two and further reduce the programming difference between the apps.
It makes zero sense for rt to be replaced. Other than for you who seem to want it to die, for no reason, other than you personally don't like it.
However I wouldn't be surprised if the mini is atom, as every other mini is atom based, it all depends of its marketed at consumer or enterprise.
With each windows update 100s well last one was several thousand of extra API are being added to metro. Rt and x86