I'm not sure about that. If the destination is in a chunk that has been unloaded, there's no way to touch that chunk, to add data to it, or to load it in order to make those things happen. You can transport a player there, because that will load the chunk, but items, no, probably not.
Also, if the portal is both-ways, how would you handle the items? should they cycle between the places periodically, or should they transport once? If they should transport once, how do you tell that they have already transported?
Also, if the portal is both-ways, how would you handle the items? should they cycle between the places periodically, or should they transport once? If they should transport once, how do you tell that they have already transported?