I think the time to start worrying about film is when you can no longer buy it, except at camera stores. About the only film I've seen that's getting tough to buy here in the USA at various convenience/mart/grocery stores is consumer 100 color neg film, and true BW film. I still see even K64 on the racks.
Once I can no longer buy at camera stores, I'll buy some istD derivative. Hopefully, by then, Pentax will have made several such beasts. And I might even be able to get a model that doesn't require a Pentax Function and an extra step to use K/M lenses.
Digital, shmigital.
