One thing that does not seem to be talked about much is that all rare earth metals will be completely depleted, in any practically extractable reserves, within the next 50-100 years. The problem with these kinds of projections is that they almost invariably forget to take technological change into account; Malthus predicted that humanity would starve to death because of food shortages in the late 18th Century, whale oil was unsustainable until the discovery of underground oil, and horse shit threatened the viability of cities until the development of the automobile (which then threatened cities through emissions), and various people have predicted peak oil at various times going back to the early 20th Century.
Now, we will eventually face peak oil, but that date keeps getting pushed further back due to advances in extraction technology. But by then hybrid/electric cars or other, unforeseen technology may have rendered the point moot. Rare earth metals might be completely depleted in 50 - 100 years, assuming that the ability to find and recover such metals doesn't improve and that recycling technology doesn't make original harvesting moot (imagine if someday all the technological garbage we've shipped to China and Africa makes those countries rich through the trace metals that become recoverable).
This isn't to argue that we should wantonly strip mine every metal deposit conceivable, or that just because false alarms sounded in the past doesn't mean true alarms won't sound in the future. But the fairly long history of worries about resource depletion, followed by the obviation of that resource or by the discovery of new deposits, means that I don't think most of us should be wildly worried about the possibility that rare earth metals will disappear in 50 years.