Verse 14: Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory. It is important to remember that verse 13 ended with a comma. Both together read Ye were sealed with that holy Spirit of promise, which is the earnest of our inheritance. In other words, we were sealed, or promised to be preserved, in the same way that Israel was.
Again, notice that he wrote our inheritance. and not your inheritance. Just as God sealed them, he has sealed us. So, primary point of the verse is not the inheritance, but the sealing. We both have the promise of preservation if you will.
To me, this has to be because of what he already clearly stated in verse 11 they have obtained an inheritance, being predestinated according to the purpose of him who worketh all things after the counsel of his own will. Realistically, the church does not have an inheritance because we are not the heirs (we already talked about that), but we, like them, have the promise that God will protect us just like he promised to protect them.
Notice, that it says until the redemption of the purchased possession. What I find interesting is that the word translated redemption is apolutrosis and it is only used ten times in the KJV and three of them here in Ephesians. It is a compound word which means the act of ransom.
I find it significant because who normally pays a ransom? - The one to whom it belongs. Israel is the purchased possession that was ransomed. Exodus 15:16 says Fear and dread shall fall upon them; by the greatness of thine arm they shall be as still as a stone; till thy people pass over, O LORD, till the people pass over, which thou hast purchased. This can also be seen in verses like Deuteronomy 32:6; 2 Samuel 7:23; Psalms 74:2) And he purchased them to the praise of his glory.
Of course, I believe while the direct interpretation of the verse is Israel, it also has application to us in the Body of Christ as well in that we too have been bought, not necessarily ransomed. Paul told the Corinthians For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's (1Corinthians 6:20) and Ye are bought with a price; be not ye the servants of men (1 Corinthians 7:23).