The bar to entry for manufacturing photographic film, especially color film, is high. There is zero chance of a low-budget garage-based company to get off the ground. This is primarily due to the complexity and regulatory requirements of manufacturing color film.
Black & White film may well have the opportunity for small-scale non-commercial manufacture, based on actual experience from people like Ron Mowry. How this translates to commercial activity is unknown.
Existing small-scale manufacturers, particularly in countries where emissions/pollution standards are low or non-existent and costs of labor are low as well may well be able to continue for some time after the bigger companies like Kodak, Fuji (and to some extend, Ilford) withdraw from film manufacturing, but a) they do not make color film and b) they're not likely to.
For these reason, I can foresee B&W film remaining available for some time into the future, but color film having a fairly short period of commercial availability remaining.
Comparisons to other obsolete manufacturing such as LP records and buggy whips are not useful, because the bar to entry into such fields allows a relatively small financial outlay and low or no regulatory standards requirements be met.
Statements such as 'where there is demand, there will be supply' are not accurate either. Supply is often exhausted before demand ceases, and although sufficient demand will reignite supply, the question is always 'at what price'? Recent events such as the attempted restart of the Polaroid manufacturing process for integral film shows that two things are required besides demand. First is one or more extremely motivated individuals who have more than a profit motive, and second is sufficient capital outlay. If the "Impossible Dream" project succeeds, we will then move to the phase where one finds out how many people will line up to pay $100 (for example) for a pack of integral film - and keep coming back for more.