When you get to the point that you can't compete with the little tiny cameras and the great big cameras, you're in trouble. You being not only Leica, but us folks who like to use their cameras. And that, to me, is kind of sad.
I think the biggest threat to Leica, is Leica. Snobbery, hubris and arrogance usually becomes ones undoing.
But for the moment while most of their traditional customer base can no longer afford a digital M, they have gained a lot of new customers who have money to burn. The order-books are full and they can't keep up with demand for the M9. Leica seems to be pretty content to sell about 12,000 bodies a year and apparently that is what they are managing to do. So, from where they stand all is well and that probably holds true if you are comfortable with the status quo.
The irony of course is that a large part of the Leica mythology and status comes from the artists and photographers who have used their cameras over the past 80 odd years. And with a few exceptions most of them were not members of the local country club.
HCB has probably inspired more people to plunk down the cash for a Leica than anyone else in history and he's never even appeared in an ad for the company.
Yes, a few wealthy pros will still be able to afford them and quite frankly you only need one or two of them to feature in a shiny brochure or occasional exhibit. But it is a sham. For the most part the future photographic record of Leica will be vacation pictures, found color and shapes, pets, airforce resolution charts and shots of children and holidays.
So, what to do? Yes, you can always buy used, but you will probably always be trailing by one model, because the prices won't come down considerably for used examples of a body that is still in production.
You can hope and pray that Leica comes to their senses an announces a second cheaper model (APS-H). But IMO you can hold out one hand and spit in the other and see which one fills up first, before that happens.
Or you can just write Leica off. Bill is right. There are a lot of alternatives flooding in to the market at the low end. They may not be as elegant a solution as the M, but they are a viable alternative and are improving at a breakneck pace. I'm not buying an M9 for several reasons and I will probably also skip the X1. But the M43rd cameras, G11/S90, Ricoh GRD III and new GXR are looking mighty tempting.
Being a cult brand can be difficult. Smart companies know to harvest this resource and thrive (harley&Davidson, Apple, Porsche etc). These customers identify with the product on a personal level and develop an unusual level of loyalty. The problem is of course that things can get ugly, if they feel betrayed, because they tend to take it personal. But like I said, the order-books are full and I don't think Leica is losing any sleep about that.
My advice? Use Leica for when they can supply what you need as a photographer and find alternatives for when they fail you.