According to Les, when will the end come in relation to preaching the gospel to all nations?
The end will come only after the gospel has been preached in all the world as a witness unto all nations. Every nation, tribe, and language will be reached before Christ returns; then, and only then, shall the end come.
Les explains that the gospel will succeed in touching every nation, tribe, and language before Christ returns. He points out how all-inclusive this is: the gospel is preached in all the world for a witness unto all nations, and then shall the end come. So the end follows the completion of that worldwide witness, not before it.