Also, we might have a far better recycling technology in 100 years and will know where to find the material. Perhaps it is better to simply store it somewhere for the future. Only now we should make sure it doesn't find its way to the oceans.
Most trash heaps from 100+ years ago have something of value in for people today (antiques, museum artifacts, leftover gold/metals in mine waste, etc.).
It seems unlikely that today's trash heaps won't have something of value for future people.
The only challenge is how to stop leaching of poisonous stuff...