But the real threat is Canon simply disabling the 3rd party loader ML uses. As you might know, the ML "firmware" just patches one byte so that their "autoexec.bin" is loaded from the card - probably the same mechanism Canon uses for in-house fw development. There is always going to be someone with too much time on their hands willing to take up a challenge.
The challenge would involve opening your camera, unsoldering the firmware chip from the pcb and replace or reprogram it as it's done with hacked game consoles. If there's no software way to enable 3rd party code, that's it for 99.9% of the current ML users.
The reason ML devs didn't bothered with the 1DC have probably more to do with hassle, lack of access to a 1DC body, and having to support it,
Nope, Canon told them not to touch the 1dx or else, see the ML forum where this is stated for all to read. It's pretty easy to say "Well, any lawsuit will be dismissed anyway" from an armchair approach, but if you're the private individual w/o any law insurance being actually sued it might be another perspective altogether :-o
Last not least, and I'm happy at least the main ML dev is there with me, ML isn't made to pimp rich people's 1d gear for free or backport 1dc->1dx features. It's an enthusiast's project to expand the possibilities of low to midrange gear that limit creativity because Canon designed them with your Mom as a user in mind. In that spirit, the hilariously expensive €3000 5d3 is the absolute top of the line that qualifies for ML support.