If you socket one of your items with something will you be able to remove whatever it was you put in that socket? In diablo i could never figure out how to do that if it was possible >.>
The last stated ability planned is to allow you to overwrite a gem with a new one, destroying the original. This would of course allow you to continue upgrading an item as you happened upon more powerful gems.
For reference (in case you still play), in Diablo 2 you could use 1 Hel + Scroll of Town Portal to destroy all gems/runes/jewels in the item. There was no way to replace them one by one.