As has been pointed out, God did not forsake the House of Israel, but Israel had forsaken their everlasting covenant with God which He made unto their fathers Abraham, Isaac and Jacob, which of course was intended to include all the posterity of Jacob or Israel. In their apostate condition they forfeited their promised blessings of that covenant.
I think it is important to remember that in the blessings pronounced upon each of the twelve sons of Israel, that two of those sons were given greater blessings than their brethren, namely Judah and Joseph. One should also consider the further blessings pronounced upon the sons of Joseph, Ephraim and Manasseh. Out of the loins of Joseph was to come a multitude of nations. We should also note that Joseph was to be a fruitful bough and that his branches were "run over the wall" and that his posterity would also be "separate from his brethren". Ephraim was to "be sifted among the nations".
We should also remember that it was through the lineage of Judah that salvation would come. All are therefore indebted to the Jews, not only for the faithful keeping of the records of the Old Testament, but also of the New Testament. Our greatest indebtedness to the House of Judah is for salvation itself. For without the atonement of the Messiah, there would be no salvation or resurrection for anyone.
The Bible is also very clear that God has not forgotten His covenant with Israel, and has indicated that after their long dispersion , that the time would come that they would in the latter days begin to remember that covenant. They would repent and return unto the Lord and again receive a restoration of their promised blessings as prophesied.
Veteran pointed out this powerful point from Ezekiel:
Ezekiel: 37:21 And say unto them, Thus saith the Lord GOD; Behold, I will take the children of Israel from among the heathen, whither they be gone, and will gather them on every side, and bring them into their own land:
22 And I will make them one nation in the land upon the mountains of Israel; and one king shall be king to them all: and they shall be no more two nations, neither shall they be divided into two kingdoms any more at all:
23 Neither shall they defile themselves any more with their idols, nor with their detestable things, nor with any of their transgressions: but I will save them out of all their dwellingplaces, wherein they have sinned, and will cleanse them: so shall they be My people, and I will be their God.
24 And David My servant shall be king over them; and they all shall have one shepherd: they shall also walk in My judgments, and observe My statutes, and do them.
25 And they shall dwell in the land that I have given unto Jacob My servant, wherein your fathers have dwelt; and they shall dwell therein, even they, and their children, and their children's children for ever: and My servant David shall be their prince for ever."
Perhaps what should be of far greater import and interest to all christians today is the huge amount of scripture which pertains to the gathering of the House of Joseph and the gathering of the House of Judah. Along with those two separate gatherings is also the restoration of the "Ten lost tribes" to their respective promised lands.
We should remember that the return of the House of Judah to their promised place in the land of Palestine is an ongoing "work in progress". We should also remember that this gathering pertains to only one of the tribes of Israel.
Also in these latter days is the process of gathering the descendants of the House of Joseph who were as the scripture says "sifted among the nations". The House of Joseph will be gathered to their "promised land".
the third aspect will be the restoration of the ten lost tribes from the land of the north, where the Lord had taken them.