Sawzaw, the war is not really about the Taliban, just like it was not really about Al Queda (which barely even exists, except for American propaganda purposes). It's about the USA securing a very important piece of strategic territory which lies across very important passes that allow access to Russia, China, India, Pakistan, and Iran. Major empires have been fighting over that piece of land and trying to control it for thousands of years, but they have all failed to impose their will upon the indigenous people, the Aghans. The primary force opposing the USA is the Pashtuns, a tribal people who are the majority in southern Afghanistan and northern Pakistan. They used to be known as "Pathans", and are famous for being good warriors. Some of them are Taliban, some are not.

The USA/UK/Canada is simply the latest imperial order to attempt to do this, and they will fail, as the Russians failed before them.

The Taliban are one among a number of factions that might succeed in dominating Afghanistan after the Allied Coalition leaves. There's no guarantee that the Taliban will be the winner in the struggle that follows, but someone in Afghanistan will be the winner.

As for the opium trade, it's basically the only way that most of the country people in Afghanistan can earn a living, so that's why they are doing it. They have always done it, and they will continue to do it. The Afghan forces that have allied themselves with the USA love dealing opium, so nothing is going to change much in that respect regardless of whether the USA stays or not. Opium will continue to be sold from Aghanistan. That is a fact of life.