Item anchors are already symmetric (support for both anchors.left and anchors.right), but it should be possible to easily mirror the direction of the defined anchors. See attached patch mirrored_anchors.diff for an example implementation and layoutsamples.zip for an example QML code. See parent task QTBUG-11042 for more info about QtQuick right-to-left locale support.

Item {
    LayoutMirroring.enabled: true
    anchors.left: parent.left // left becomes right
    anchors.leftMargin: 3
}