أُعِدَّتْ is a feminine singular passive perfect verb: “was prepared.” It provides a textual basis for the already-existing abodes. Yet Arabic can sometimes use perfect forms for an assured future event, so the linguistic point should be read together with the wider evidence.
The apparent sense of the expression and a suggested alternative interpretation are not the same evidentiary claim. The mere possibility of reinterpretation does not by itself cancel the apparent sense.