Too much of anything can be toxic. Just googled toxicity of Indium and it is toxic if in the bloodstream. Is it less toxic than Cadmium, so its ok? Did the focus of government regulators on Cadmium, because it was predominant in displays a few years ago prevent them from delving into the toxicity of Indium? I don't know. Indium seems to be getting a pass that was not given to Cadmium. Perhaps in a few years, there will be a groundswell for Indium to be reclassified and a less toxic solution found? I think it will be Silicon, and I think it will happen organically, as a next generation material as it becomes better known. Right now there is demand for Indium and none for Silicon QD.

Regarding disposal in landfills, displays use less than one gram per square meter quantum dots, so I believe there will come a way to recycle the plastic or glass for other purposes.

BTW, Indium is key part of ITO, which is in all electronic displays as a cathode type material. There are alternatives already being readied to take its place as cathode material. Indium is also used in IGZO displays and solar cells so perhaps someday because of expanded uses it will be more expensive and less available. I don't know.