There is no chapter break here. The thought should be continued directly from Revelation 10:11 - "You must prophesy again about many peoples, nations, tongues, and kings." Then He says, "Rise and measure the temple of God, the altar, and those who worship there."
We see a dual commission: First, to go to kings, nations, and tongues, a broad and general commission. The second one is more specific - focused on the Temple, the altar, and the worshippers. This two-pronged approach is seen throughout the Scriptures. There is 1) a message to the world, then 2) a message to the church.
The second part, measuring the temple, the altar, and the worshippers, can be equated to what we call, in these times, "feeding the flock." The first, going to the world, we call "preaching the gospel." These two areas of preaching are never sundered from one another. In fact, one cannot be done without the other because they always overlap in some bit. They should be done in tandem.
Sometimes, however, one needs to be done more fully than the other or must be emphasized more, as God directs. God likes them to be done simultaneously, if possible. There is a great deal of work that needs to be done. The church must make a witness. Then, the ones whom God calls to do and support the work must be fed to grow and overcome to be part of His Kingdom. They must be helped to overcome and to go on to perfection. So these two things have to be done. If a person starts preaching the gospel to the world, pretty soon he will have people following his message, and they will need to be taught further and brought along.
One can preach the gospel all he wants, but nothing will be done with the fruit of the gospel unless he is also feeding the flock. They must be done in tandem. They do not necessarily have to be done 50 percent each, but they will be done because God's purpose requires them both.