hm... I think it would be more fitting if gear ilvl from 51 to 60 progress from ilvl 90 to 140, so at lvl 51 you can have gear of ilvl that at least lets you enter current endgame dungeons,then progress so at lvl 60 standard/questable/purchasable gear to be better than the one we have now but the new gear for lvl 60 dungeons/raids and the new AF to jump to ilvl160~180

so in rough numbers...
lvl51-ilvl90
lvl52-ilvl95
lvl53-ilvl100
lvl54-ilvl105
lvl55-ilvl115
lvl56-ilvl120
lvl57-ilvl125
lvl58-ilvl130
lvl59-ilvl135
lvl60-ilvl140-raids ilvl160-180