Mordekaiser is confirmed to be getting another rework at some point. Vladimir and Malzahar are certainly in better spots than before their reworks because they're actually seeing play rather than being considered troll picks (legit I was once reported for trolling because I simply picked Vlad top before the rework).
Let's take a look at the least successful rework among these, Mordekaiser, vs the Kog'Maw rework:
Mordekaiser:
Attempted to force him into an awkward role (melee bot lane carry)
Only worked at first because they made him literally busted
Got nerfed down a bunch because Riot realized it was terrible but also realized that Mordekaiser shouldn't just be reverted into his previous form (which was also super nerfed for balance reasons)
Kog'Maw:
Protect the Kog'Maw comp
Made him MUCH too much of a monster late game
Pre-Rework Kog did the thing that they wanted from the Kog rework without it being literally a guaranteed win if you let Kog get to 3 items unless Kog's team is trolling/intentionally feeding
Also note that the only change being reverted is the W giving him doubled attack speed and doubling the cap
They both have similar problems for game balance, but Kog's rework can be solved by just reverting the W change. Mordekaiser likely needs a full VGU to get him into a relevant spot without being busted.