Sorry, but there are none. Those that you have mentioned, are pretty much what we have for the moment. Some would say EvE Online, but that's not fantasy, nor medieval. You have Mortal Online, that fits your description, but that game is pretty much trash, if you ask a lot of players (I can't say anything about it, because I have not tried it). Also, there is Xsyon, which is more like Wurm Online. But, here aresome few sanboxes that are coming in a "near future":
* Origins of Malu
* Xsyon: Apocalypse (next part of the game)
* ArcheAge
* Ember of Caerus
* The Repopulation
* Greed Monger
* Pathfinder Online
I am currently looking forward to The Repopulation, Greed Monger and most of all: Origins of Malu!
EDIT: Forgott Darkfall: Unholy Wars and Everquest Next! The problem is, that Darkfall isj ust like a open big PvP arena and not som uch PvE sandbox elements and so on, BUT Everquest Next WILL be the No.1 mmorpg in the future, IF they can nail everything! Proof: EQ1 and EQ2 are great games!
Comments
In addition to these future releases: This Thread: List of Sandbox MMORPGs
http://www.gdcvault.com/play/1014633/Classic-Game-Postmortem