Dear Aurelien,
The difficulty in 'new' film products is the return on investment and the nett increase in sales, so often what actually happens is that the sales are just diluted across the range, not increased, and whilst we would love global monochrome film sales to increase they are not at present.
Simon,
Even if the total market does not expand when you introduce new film, would new film cut you more market shares, say from Kodak, Foma, etc? I imagine the film market as a whole is still very large and profitable and will remain so for some years to come. So it may still be a good thing to do? Look at the auto industry: everybody knows oil is doomed, probably run out in 20 years, or price go sky high or suffer from punishing environment control levy, yet all these car companies keep designing new cars. I won't pretend to know business better than you, but if you can recoup your investment in a few years and possibly earn couple more years of profit from it, it may still be worthwhile to do.
Also, have you looked into the Chinese market? Digital cams are comparably very expensive there (I have first hand knowledge of this.) While many areas are at par with developed countries in terms of technology usage, the vast majority, here we are talking hundreds of millions of people, don't own or use computers. So traditional film is still more convenient for them. Even if you could get film to just one tenth of them, it could be bigger than the rest of the world put together. Then there's also India.
These countries have unlimited purchasing power (China is already #3 economy and poised to surpass japan any time now), and at the same time they are very insophisticated about how to spend their new found wealth. So there may be great opportunities for you there. Most of those who dared to try their hands in China ended up succeeding beyond their dreams. Getting into China may be easier than you think! Once you do, volume would be assured.