"In those days the house of Judah will join the house of Israel, and together they will come from a northern land to the land I gave your forefathers as an inheritance." NIV translation
During this reign, all of God's people will be united in His land. This will include all of the tribes of Israel as well as the Gentiles. This is only possible because of the grace of God displayed through Jesus Christ.
"'I myself said, "How gladly would I treat you like sons and give you a desirable land, the most beautiful inheritance of any nation." I thought you would call me "Father" and not turn away from following me. But like a woman unfaithful to her husband, so you have been unfaithful to me, O house of Israel,' declares the Lord." NIV translation
Throughout the Old Testament, individuals never heard that they would call God their "Father" as they were treated collectively as a nation of God. Here, God says that, He was ready to have them call Him "Father" and to treat them like sons. But, like a woman who cheats on her husband, they have turned to other gods. This promise is for us today through Jesus Christ as He made the way for us to be children of God. As God told Israel, He wants to treat us like His children and He has given us the most beautiful of inheritance (for more details, check out Revelation 21).
"'A cry is heard on the barren heights, the weeping and pleading of the people of Israel, because they have perverted their ways and have forgotten the Lord their God.'" NIV translation
This verse speaks of repentance which is a changing of the mind. The weeping and pleading is an outward expression of this inner change. The people have realized that their ways are wrong and they are now far from the Lord.
"'Return, faithless people; I will cure you of backsliding.' 'Yes, we will come to you, for you are the Lord our God.'" NIV translation
We see, here, the conversation between God and His people about the cure for backsliding. The calf we talked about in verses 4 & 5 can simply stop digging its feet in and decide to follow the man's direction. It is the same for God's people to return to Him as we simply need to stop digging our feet in and accept the direction of the Lord.
"Surely the idolatrous commotion on the hills and mountains is a deception; surely in the Lord our God is the salvation of Israel. From our youth shameful gods have consumed the fruits of our fathers' labor - their flocks and herds, their sons and daughters. Let us lie down in our shame, and let our disgrace cover us. We have sinned against the Lord our God, both we and our fathers; from our youth till this day we have not obeyed the Lord our God.'" NIV translation
This realization of the need to stop digging our feet in is called repentance. Here, we see Israel recognizing that they were deceived and changing their mind to agree with God. This is what is meant by repentance and it is the same thing that we all have to go through to get to the point of accepting Jesus Christ as our Lord and Savior. In order to fix a problem (sin) you must first admit that you have it and desire to change.