I think it would be next to impossible to completely eliminate any street drug. In the US, there definitely are high-profile government figures that truly want to take drugs off of the street. BUT, there are also a good bit of high-profile government figures that make tons of money by partnering up with major drug distributors by laundering money, looking the other way, and tipping them off when LEO gets on to them. And as we all know, the rate of drug production far exceeds the rate of drug seizure.
But I think a major drug in the future will be Cannabis, because it seems that we are just now about to slowly enter a more Cannabis-tolerant period (with Cali and all). And no doubt, pharmaceuticals will rise too, as our more recent, more educated generations will realize that the security of consistent pharm-purity and dose-indicators make them superior to unknown factors about street drugs.
Let's also not forget that "Synthetic Life" has recently been created (Discovery channel), which allows computers to create designer genes with very specific functions---this will allow the development of many new drugs using these programmed cells.
I think DMT will eventually have its time of popularity. When science evolves enough to determine its function as an endogenous neurotransmitter, I believe this function will have something to do with higher-perception of meaningful information, which will entice more people into exploring it. If only the "DMT: The Spirit Molecule" documentary can get finished and released, it may provide the little 'kick' DMT needs to lift off. One can only wish.