> I haven't seen the article, but I don't buy it, there's no likely events that will harm Voyager 1 and 2 in that time period, for instance.

Sure, but nothing will encounter or observe them ever again.

Things we put into heliocentric orbits are likely to be forever, too.

> Along a similar vein many of the satellites that we put in graveyard orbits around earth at the end of their useful life will also plausibly last that long, though there is a lot more debris for them to collide with.

While they won't decay from drag in a few million years, tidal forces and photon pressure become significant over time.