Well, I suppose so. Our constitution won’t last forever, and someday we might be living in a state where the human rights we take for granted no longer apply.
In such a state, who knows what the legal status of clones would be?
But the problem then isn’t that clones are slaves, the problem is that HUMAN BEINGS are slaves. A society that declares clones to be slaves is a society where the human rights of anyone can be taken away on the whim of the powers that be. Sure, this could happen. But of course, there are plenty of places in the world today where this is already true. Burma, Sudan, Saudi Arabia, and so on and so on. We don’t have to imagine it, it’s already true.
But suppose you were a clone born in Burma. And stipulate that the Burmese government is illiberal, and doesn’t give a crap about human rights. You could end up a slave. But the problem is not that you’re a clone, because the same problem exists for every citizen of Burma. Everyone in Burma is a slave. And there’s no reason to imagine that the government of Burma would have any interest in harassing clones in particular. What’s in it for them? Of course, various oligarchs might raise clones as organ donors for themselves, but the suffering of two or three clones in such a scenario is pretty much drowned out by the suffering of the mass of Burmese citizens, it vanishes into the background noise. Those Burmese oligarchs have people killed every day.
The bottom line is that there is no particular reason to imagine that clones will be singled out for abuse in the future. Slave soldiers or laborers take 18 years to grow to maturity. If you want soldiers it is far easier to conscript 18 year old kids. If you want laborers there isn’t exactly a shortage of poor people willing to work for peanuts. And the vast majority of people in the world never have a disease that would be cured if only they could get an organ transplant. Sure, some do, but most people die of accidents or diseases that couldn’t be helped by an organ transplant. So how many future sociopaths are going to raise clones of themselves, on the off chance that they might someday need a liver transplant? It could happen, but the notion that in the future there will be a large number of cloned organ slaves is implausible.
If this imagined future world is wealthy, they have no need of slave laborers or slave soldiers, or slave organ donors. And if they are poor, these slaves are going to be so expensive that only a very small number of people could afford them, and be sociopathic enough to want to create them, and have the foresight to create them years and years before they are needed.