i guess you can wait another 2 years if not longer before you see that on a imac, as all these three would sky rocket the price for a imac beyond the £2000 mark and push it closer to £3000 , as there is only space for one harddrive inside and nobody would accept a single ssd with only 64gb ,i guess 500gb is a must in a modern computer, otherwise you would need to invest in another external drive and clutter up your desk , and the whole point of a AIO is a clutter free desk ,for the other things it would need another back for the connections and rearranging internal organs of the imac and another logicboard .....
another thing osx does not support usb3.0 as far as i know , so it would need a update of osx too on top of the above mentioned things