God made other covenants, whether it was to a man or to nations. This is a rather simplistic view that is based on ignoring the other covenants. Did God null the covenants He made with Abraham, Israel, David, and other people end because of Jesus' sacrifice? No.
Anyone making this kind of argument can't just offer a nice-sounding platitude and logically expect anyone wto co-sign on it. God is still working with Israel, He is still keeping the promises He made to Abraham concerning his descendants, He is still keeping the promises He made to David, God's Sabbaths are still a sign that someone is following Him, and He is still keeping the promise that He made to Noah, no matter how evil this world becomes between now and Christ's return.
God doesn't subscribe to this kind of asinine reasoning, and it's certainly not supported the Bible. In all of the OT prophecies where God prophesied that He would scatter the Israelites among the Gentiles, not once did He ever say that they would be excluded from the promises.
Any person or nation that can trace their physical ancestry all the way back to Jacob is an Israelite entity. Whether they practice the Hebrew culture or not is completely irrelevant because God promised in Jer. 30 that David is going to eventually rule over every last physical Israelite once Christ returns.
The missing tribes are only "lost" as far as the world is concerned because people don't believe God and they can't be bothered to do any research about where those tribes went once their Assyrian captivity ended. To God and anyone else who have put in the time to prove where those tribes went, they are anything but lost.
The fact that the prophecy Moses gave in Deut. 31:29 is playing out right now in the countries that descended from those 10 tribes inherently proves that God still considers them tribes to be Israelite heirs, otherwise they wouldn't be experiencing the rather specific curses that God said was going to come on their descendants for disobeying what was written in the Law.
In God's New Will and Testament, all covenants and promises are fulfilled only in Christ, and in those who are in Christ.
The OT covenants and promises are the promissory clauses of God's Old Will and Testament, and they are both revoked and fulfilled in the promissory clauses of His New Will and Testament, written in the Blood of His Son Jesus Christ, the Divine Testator, coming into full force and effect upon His death.
If you have made your own Will and Testament, you will see that the very first clause states the following or its equivalent:
"I HEREBY REVOKE all former Wills and other testamentary dispositions by me at any time therefore made and declare this to be my Last Will and Testament."
This means that all former wills and testaments, and all of their promissory clauses in their entirety, are completely null and void. In their place, the promissory clauses of the current last new will and testament are the only ones in force and effect. Any promissory clause which appeared in the old will and testament, but does not appear in the new will and testament, is irrevocably null and void unless yet another new will and testament is made which re-includes it.
Thus we see:
Hebrews 9
15 And for this cause he is the
mediator of the new testament, that
by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
16 For where a testament is, there must also of necessity be the
death of the testator.
17 For a
testament is of force after men are dead: otherwise it is of no strength at all while the testator liveth.
Hebrews 10
9 Then said he, Lo, I come to do thy will, O God. He
taketh away the first, that he may establish the second.
Hebrews 8
13 In that he saith, A
new covenant, he hath
made the first old. Now that which decayeth and waxeth old is ready to
vanish away.
God`s New Will and Testament is everlasting:
Hebrews 13
20 Now the God of peace, that brought again from the dead our Lord Jesus, that great shepherd of the sheep, through the blood of the
everlasting covenant.
There is none greater.
We see other new promissory clauses of the New Will and Testament in:
Matthew 21:33-45
In this parable, the son, who is identified as the heir, typifies
Christ.
Galatians 3:16
Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is
Christ.
2 Corinthians 1:20
For all the promises of God in
him are yea, and in
him Amen, unto the glory of God by us.
Hebrews 1:1,2
1 God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets,
2 Hath in these last days spoken unto us by his
Son, whom he hath appointed
heir of all things, by whom also he made the worlds;
In them, we see that the Heir and Beneficiary is
Christ alone, that
all of the promises are affirmed and confirmed in Him, and that He is Heir of
all things.
All includes the OT
land promises, the
restoration promises, the
blessings promises, and
all else. There are
no exceptions.
If you deny that God has appointed His Son
heir of all things, you declare God to be a liar.
His New Will and Testament contains even better promises:
Hebrews 8
6 But now hath he obtained a
more excellent ministry, by how much also he is the mediator of a
better covenant, which was established upon
better promises.
Such as:
Hebrews 11
16 But now they desire a
better country, that is,
an heavenly: wherefore God is not ashamed to be called their God: for he hath
prepared for them a city.
Additional promissory clauses in...:
Romans 8:16-17
16 The Spirit itself beareth witness with our spirit, that
we are the
children of God:
17 And if children, then
heirs;
heirs of God, and
joint-heirs with
Christ; if so be that we suffer with him, that we may be also glorified together.
Galatians 3:29
And if ye be
Christ's, then are ye
Abraham's seed, and
heirs according to the promise.
...declare that we who are in Christ are joint heirs with Him.
But notice:
There are no promissory clauses for anyone, Jew or Gentile...
Who is not in Christ.