[However, many things could slow this downward trend from legislation to a strong surge of interest from people who are about five years old right now, for their own reasons. What you suppose will happen seldom does.]
If it resisted at least 10.000 years I think it might change but quality tobacco smoking won't disappear.
I make an analogy with fountain pens (of which I am a collector), they virtually disappeared in the fifties-sixties but in the last 25 years they reemerged. Yes, you don't see them anymore in practical life (as you don't see pipe smoking outside for the most part) but there is a renaissance of fountain pens, as a matter of fact you have now the best, most expensive and most variety of pens/inks/paper ever made. The number of users is much smaller than in the past when they were a commodity, now they are just for the conosseurs. Something similar could happen to pipe tobacco, there are many things related to it, meditation, relaxation which I don't see it disappearing. Possibly it will be different from now, maybe will be limited to high quality expensive blends, but I think it will stay for a long time even if maybe in a different form from now.