Genesis 48:21 And Israel said unto Joseph, Behold, I die: but God shall be with you, and bring you again unto the land of your fathers.
Jacob knew that God would keep His Word. He tells Joseph that God will be with him and take the people back to the promised land. It will be 400 years or so but God will keep His Word.
One thing you can know as you study the Bible is that God keeps His Word. He says something and He means it. It may be many years latter but He will come through. It may not be in your life time but He will come through.
Trust the Word of God with your life. If you claim to be a born again Christian then you are already claiming to trust Him with your eternity.
So trust God to keep His Word!