Extremely Likely, Yes.
As it stands, there is no indisputable canon instance showing the transfiguration of a living human being into an inanimate object.
According to the books, Human Transfiguration is a very tricky and difficult sub-branch of Transfiguration with lot of potential to easily go wrong. Students at Hogwarts don't start learning this until Sixth Year.
We know some things about Transfiguration:
- A human corpse can definitely be transfigured into an inanimate
object. (Canon source: Crouch Sr's corpse to single bone)
- Parts of humans may be transfigured into an inanimate object. (Canon source: an article in The Quibbler)
- Transforming smaller living animals to inanimate objects seems to be an easy task to do.
Logically, it seems easy to come to the conclusion that though the human (or rather sapient - there's no reason to assume transfiguring a house-elf, or centaur, or gnome would be easier) transfiguration is much more difficult, it is highly likely to be possible, because at the end of the day, a human is still an animal and rules shouldn't be too different.
And if all else fails, and direct human-to-inanimate transfigurations are impossible in the HP world, then there's still the possibility of a two-step transfiguration - transfigure the human to an animal and then the resultant animal to the inanimate object.
The only instance in the books of an entire human-body being transfigured into an inanimate one is when Barty Crouch Jr. transfigures his father's body to dispose of it:
"When everyone was gone, I Transfigured my father's body. He became a bone... I buried it, while wearing the Invisibility Cloak, in the freshly dug earth in front of Hagrid's cabin."
However, it's worth noting that the human in this transfiguration is a dead body, and the object to which it is transfigured is something that is already a part of it. It is entirely possible that transfiguration of a corpse no longer qualifies as Human Transfiguration - we have no canon evidence to prove or disprove this.
Note: Untransfiguring Yourself aka Human-to-Armchair??
Both HP wiki and alexwlchan mention Slughorn's armchair disguise as a transfiguration. However, there's no canon evidence that it is and a lot of canon evidence that it isn't. Namely -
- Slughorn yelled "Ouch" as soon as Dumbledore poked him - a transfigured chair would neither feel pain nor be able to yell.
- We know that Animagus form is difficult precisely because it allows the animal form to retain (simplified) human thought in animal form and untransfigure themselves without the wand movements they'd be unable to make as an animal, and that humans transfigured to be animals ootherwise, do not do so. So it seems highly unlikely that this limitation would not extend to transfigurations to inanimate objects (ie. without the capability of thought at all)
Of course, #2 also means, just as in the case of human-to-animal transfigurations, it would be impossible for a witch or wizard to untransfigure themselves, once transfigured, so another wizardly accomplice would definitely be required to avoid being trapped forever as a cushy chair.