There was always a remnant in Israel. And they made up a part of the nation of Israel. You can't separate the remnant from Israel. And now Israel has been cast aside:
"For if their having been cast aside has carried with it the reconciliation of the world, what will their being accepted again be but Life out of death?" (Ro.11:15).
It was the middle wall of partition which served to separate the Israelites, the members of the commonwealth of Israel, from the Gentiles Now that middle wall has been broken down:
"For he is our peace, who hath made both one, and hath broken down the middle wall of partition between us" (Eph.2:14).
If you are right that the remnant remains distinct from the Gentile believers then the middle wall of partition has not been broken down.
As Paul said, the LORD has "made both one," not two!