The M7 à la carte is my dream camera and I expect to use it for the rest of my, hopefully, long life. But, will I be able to put a roll of Velvia or ilford through it in 10 years? What about 20? I know that film is still profitable for companies to produce; however, i worry that at some point it will become such a niche market that film will become too expensive for an average person to use.
Until now the most money I've spent on a camera has been a used M4. If I can't use it in 10 years it becomes a nice collectors item. The M7 becomes a very expensive "mistake" (not quite the word I am looking for, but you get the point.) I can't see spending $8000 on a M9 that will be obsolete in a few years. Is $6000 on a M7 a similar situation?
A lot of people stockpile film and keep it in the freezer. I don't have that much in the freezer, but it is enough to last for at least another few years, given my shooting habits.
The question of whether an a la carte M7 is 'worth it' can be answered with a thought experiment. Say you were able to shoot film for the next 20 years and then suddenly film production and development ceased. Which would you prefer to shoot with for this 20 year period, finances being amicable: a stock M4, or a M7 completely customized to your desires?
You say that an a la carte M7 is your dream camera, but you seem to put a qualifier on that, in that is is ONLY your dream camera IF you can use it for the rest of your life. Is that the deciding factor?
Leica has carefully built the image of a 'camera for life' as an appeal to traditional values, but this is a romantic notion that is, while very attractive, unfortunately a fallacy. Nothing lasts forever. Not even you. What if you reach an age where your vision cannot focus a rangefinder properly? What becomes of your M7 then?
Someone buying a Nikon D3x or Canon 1Ds Mk IV doesn't ask these kinds of questions, and they are spending at least as much money or more. That is because they are looking at the lifetime of the camera, not themselves, and weighing up the shooting experience and results with the investment required.
The M9 will not suddenly stop taking pictures when a new model comes out, so spending that kind of money is more about how long the camera itself will last, how long you will want to shoot with it, and whether its output and operation will satisfy you for that time period.
There are many DSLR's that are coming up to the 10 year mark and they are still working, and I am sure that a M9 will still be working in ten years time. Paying a few hundred dollars a year to shoot virtually unlimited photos at M9 quality is a price I happily pay. The more I shoot with it, the cheaper it becomes.
I shoot my cameras for now, and for as long as they last. Sure, I'd love a good camera that I could shoot with forever. And time passes, things change, and people change.
