That there are still twelve tribes shows that 'all Israel will be saved.'
Again, not relevant to Revelation 7, for a couple of reasons.
First, we are still in the midst of the Tribulation (at this point in Revelation), and not all who will be saved can be assumed to be saved yet.
Secondly, and more importantly, the passage you quote makes it clear that God will one day fulfill His promise of bringing Israel into relationship with Himself through the New Covenant on a National basis:
Romans 11:25-29
King James Version (KJV)
25 For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in.
26 And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob:
27 For this is my covenant unto them, when I shall take away their sins.
28 As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the father's sakes.
29 For the gifts and calling of God are without repentance.
There is a time, Paul states, when the fullness of the Gentiles will come in. That is future.
"All Israel will be saved" because only those who believe will survive.
All unbelievers are destroyed when Christ returns.
I think we see the time of the Sheep and Goat judgment given in Daniel:
Daniel 12:6-7; 11-13
King James Version (KJV)
6 And one said to the man clothed in linen, which was upon the waters of the river, How long shall it be to the end of these wonders?
7 And I heard the man clothed in linen, which was upon the waters of the river, when he held up his right hand and his left hand unto heaven, and sware by him that liveth for ever that it shall be for a time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished.
11 And from the time that the daily sacrifice shall be taken away, and the abomination that maketh desolate set up, there shall be a thousand two hundred and ninety days.
12 Blessed is he that waiteth, and cometh to the thousand three hundred and five and thirty days.
13 But go thou thy way till the end be: for thou shalt rest, and stand in thy lot at the end of the days.
In v.7 we see 3 1/2 years given. In v.11 an additional 30 days. In v.12 an additional 45 days.
What that means is that there will be, once the Seven Year Tribulation ends...75 days which fits in the Prophetic TImeline perfectly for the establishment of the Kingdom. I believe the first thrity days will be the gathering of all nations, and the Sheep and Goat Judgment during the last forty five days.
What we cannot impose into the Prophetic timeline is a concept of Christ returning and the Eternal State beginning. We see in both Old and New Testament Prophecy that there is an extended physical time after the world is judged. Ezekiel 39 and Revelation 20 are the key passages to understanding this.
The sacrifice being taken away and the Abomination of Desolation being set up coincides with Christ's Own teaching concerning the Tribulation:
Matthew 24:15-16
King James Version (KJV)
15 When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand)
16 Then let them which be in Judaea flee into the mountains:
This coincides with Antichrist being empowered, persecuting Israel, and that is for 3 1/2 years:
Revelation 12:6-17
King James Version (KJV)
6 And the woman fled into the wilderness, where she hath a place prepared of God, that they should feed her there a thousand two hundred and threescore days.
13 And when the dragon saw that he was cast unto the earth, he persecuted the woman which brought forth the man child.
14 And to the woman were given two wings of a great eagle, that she might fly into the wilderness, into her place, where she is nourished for a time, and times, and half a time, from the face of the serpent.
15 And the serpent cast out of his mouth water as a flood after the woman, that he might cause her to be carried away of the flood.
16 And the earth helped the woman, and the earth opened her mouth, and swallowed up the flood which the dragon cast out of his mouth.
17 And the dragon was wroth with the woman, and went to make war with the remnant of her seed, which keep the commandments of God, and have the testimony of Jesus Christ.
The consistency of Prophecy is simply amazing.
Continued...