There are currently a few things film does better than digital. I guess the question is, how long will it take for digital to surpass film in those aspects?
One is sensor size. You can buy an 8x10 sheet if film. For the digital equivalent, I assure you there is no such thing as an 8x10 image sensor. It would cost a million dollars. Technology would have to progress beyond silicon wafers before 8x10 sensors appear.
Regarding full frame, the up-front cost of digital is ~ $2000. The cost of a roll of velvia is, what, $20? FF digital will have to come down quite a bit before it matches the cheapness of film.
Another aspect is ruggedness. You have to keep a digital camera within a certain temperature range for it to operate properly. With film, you have a wider range, especially if you have a mechanical camera. Not sure how long it will take for digital to match that.
Yet another aspect is the capability of zero-power operation. You can expose a frame of film for six months if you wanted to, without changing batteries or keeping it plugged in. Maybe someone will invent a digital sensor that's powered by the light hitting it, but that's probably many decades away.
I don't know, do technological advances usually result in things that are inferior in some respects? The only one I can think of (not that I've researched it much) is the old Victrola. A crank operated record player needed zero power! However, electric audio technologies caught on, and nobody bemoans the fact that we can't crank our ipods.
physical sensor size- I am not convinced that a sensor that is physically 8x10 would be required to meet or exceed the image quality of an 8x10 negative. I think MF digital will end up replacing LF film, FF digital will end up replacing MF film, and smaller sensors will take the place of 35mm.
As to the expense, I am of the opinion that digital is already cheaper than film, if you shop smart and avoid GAS attacks. A 36 exposure roll of velvia is $6.25 here. 320 rolls costs 2000 dollars. That is 11,520 shots. Sure, there are plenty of GASsy people who get rid of digital cameras WAY before they accumulate that many shots, but as long as you press the shutter release button with the camera pointing at something 11,521 times, a digital body is cheaper than the film you would have put through a 35mm camera (note that the cost of a 35mm camera wasn't even factored in there). The weak link of a DSLR is the shutter, and you still get over 100,000 firings out of one.
As to ruggedness, I think there is as much difference from model to model and brand to brand as there is from film to digital. My Leica handled extreme heat better than my D700 can, but the leica HATED anything remotely resembling cold, which the D700 can handle it a bit (only about ten degrees, but still) better.
I do acknowledge your point about zero-power operation. Compared to never having to worry about it, keeping batteries charged is an aggravation. Leaving film in a camera for six months isnt really analogous though. You leave film in because the roll isn't finished. You don't have to fill a memory card before you dump it, so if you leave data on one for so long that it ends up being corrupted, it is your own fault. Also, the debate between electric and non-electric cameras has been going on long before digital was a reality, so I won't get in to that one here, other than saying that if it were somehow magically possible to get a digital camera that didnt require batteries, i would be all over it.
Unless people are specifically engineering new products to be worse than old ones, which does occasionally happen (toasters and american cars come to mind) the march of progress generally continues forward, unabated. You may not be able to hand crank a modern Hi-Fi, but you can't get surround sound out of a Victrola.
