The LAGEOS satellites have plaques that try to explain what they are without using any words or decimal numbers or similar 'current' concepts.
To me, this suggests we expect the satellites to last their full lifetime, as the technology to find them in space will surely exist in much shorter time-scales (a few thousand if not hundreds of years, when we might expect English to still be understood in some way).
But when they de-orbit I'd expect them to either burn up or be destroyed when when they impacted the earth's surface.
So: am I wrong assuming that we think they'll last their full lifetime, or am I wrong assuming that they'll be destroyed on impact?
Edit: the lifetime of these satellites is expected to be around 8m years, but for the purposes of this question lets assume that structure of the earth, atmosphere and solar system is pretty similar to now.