I have 3 links for you, from surrender@20.
First Link
This one is about the priority list. Mordekaiser is in there.
Sure, not sure who will get to on this list but champions that are high for us right now are Galio, Swain, Urgot, Cho'Gath, Irelia, Evelynn, Mordekaiser, Pantheon, Rammus, Dr. Mundo, Nunu, and Akali.
Second Link
This one confirms that Mordekaiser is in fact planned for a rework.
Mordekaiser is on our list to get a full Visual & Gameplay update one day, probably the size of Taric/Sion. We feel like the Death Knight Thematic is very strong and we aren't delivering on it very well right now. We aren't actively working on it right now though, but he is definitely on our list!
Third Link
Not much else to add on top of those two above.
With Morde it was more about doing a small gameplay update to a champion that needed a bigger update. We found that changing 1-2 abilities on a champion that probably needs a entire new kit wasn't the best strategy. Going forward we have been more careful in our class update selection and have avoided champions that really need a full VGU. This is why we skipped doing a bigger update to Swain for the Mage update (I know he got smaller changes, but not the size/scope of the bigger Mage updates). Urgot also got a small change but was passed on for a larger update for the same reason during the marksmen update.
I hope this answers your question.