For the time has come for judgment to begin at the house of God. If it begins first with us, what will happen to those who don't obey the Gospel of God?
What shall be the end of them that obey not the gospel ... ?  The "them" of this place is the secular Israel.  The introduction of "house of God," with its meaning of the true temple, makes it virtually certain that the old Israel with "their house," the Herodian temple, are those designated as the ones who "obey not the gospel."