The last sentence of Jeremiah 19:11 can be understood in two ways. Either bodies would be buried in Topheth because there was no place else to bury them; a kind of overflow for dead bodies, or Topheth would be one vast cemetery with so many bodies that not all of them could be buried.1 The difference matters little because the main point is that the Babylonian invasion is going to lead to such devastation that the city will be so overwhelmed by dead bodies that they will be unable to bury them, and many would end up in Topheth where they would be food for birds and wild animals.
11 and shall say to them, ‘Thus says the LORD of hosts: So will I break this people and this city, as one breaks a potter’s vessel, so that it can never be mended. Men shall bury in Topheth because there will be no place else to bury.