Over the weekend, Kwame Anthony Appiah asked what "future generations [will]  condemn us for." He suggested industrialized meat production, treatment of the elderly, the prison system and abuse of the environment. I'd add reparative therapy for homosexuals; and the torture regime conducted under the administration of Bush and Cheney. Douthat adds another: "that a century or so hence, breakthroughs in laboratory-created meat substitutes will have put an end to the killing of animals in general" and that this change will make "present belief in the moral acceptability of meat-eating seem hopelessly barbaric":

Note, though, that I’m envisioning a technological leap as the catalyst for this shift.

... The cotton gin launched a thousand pro-slavery polemics. The birth control pill convinced millions of people that the old moral consensus on sex and marriage was outdated and even absurd. The idea of legal abortion became more popular as the procedure itself became safer but then opposition to abortion stiffened as medical science gave us a clearer picture of life growing in the womb. The moral arguments for vegetarianism and veganism have gained ground in the contemporary West because subsisting on those diets is easier for modern Westerners than for many earlier peoples.

Wilkinson's crystal ball is a bit foggier:

My suspicion is that most of us would be quite surprised by the things our grandchildren will condemn us for, and that the more our predictions amount to praise for our current, farseeing moral enlightenment, the more sceptical we ought to be.

Tyler Cowen suggests "an alternate query, namely which practices currently considered to be outrageous will make a moral comeback in the court of public opinion." Electro-convulsive therapy comes to mind.

(Photo: Inside barren, restrictive gestation crates, pregnant pigs are unable to turn aroundor even move more than a step or two. For nearly four months, they languish in these cruel enclosures. Pigs have the same intelligence and emotional development as dogs. From the Humane Society Of The US.)