I think they mean that in the future you'll be able to hotplug HDD's and PSU's without opening the server case and have them dynamically added to the servers configuration so you can use them without rebooting!
Oh, wait. We've been doing that for ages. :/
Maybe Gartner will be right with a prediction for once. Even if it is predicting that "in the future, we'll have functionality that we already have had for decades".