Richard, it will not cost them anything. Leica has moved on to the M9, and so "failure" to support a camera they will not be manufacturing or distributing for sale is actually saving the company the cost of continuing support. Quite the contrary to their hype, yes. Hype is hype. Cost economics are evidently more compelling. This may be regrettable from the point of view of someone who thought that a digital camera could be a life investment, but there is nothing that suggests there will ever be one that will be obsolescence free.
You don't seem to be a gullible sort at all, so I'm surprised that you think there will some form of market justice meted out to Leica. This makes little sense. The market told Leica to make a full-frame digital RF, if anything. They did it. They're selling them. That's what enterprises do.
This is no different than the practice at Canon, Nikon, or any of the larger digital camera makers. The Canon 1D and 1Ds I used to own haven't seen a software upgrade in several years now. And you can buy a serviceable 1D today for less than 1/10th the price of one 6+ years ago. All good, if you like used markets for gear, as an aside. Knowledge of industry practice does suggest that Leica would behave similarly once it began to participate in the much less mature market of sensor-based imaging. So no surprise, really. My M8 is losing value as I write. And I'm aging too. At least I'm not dead and my M8 still takes good pictures.
Best to you.