It could be seen as hersey, at the least one large doctrinal error in placing the new covenant as yet future and only applicable to Israel.
According to Dwight Pentelost:
Thirdly, that the Old Testament teaches that the new covenant is for Israel is also seen by the fact that in its establishment the perpetuity of the nation Israel and her restoration to the land is vitally linked with it (Jer. 31:35-40)… Thus we conclude that for these three incontrovertible reasons, the very words of the text, the name itself, and the linking with the perpetuity of the nation, the new covenant according to the teaching of the Old Testament is for the people of Israel.4
Pentecost, J. Dwight. Things to Come: A Study in Biblical Eschatology (Kindle Locations 2285-2289). Zondervan. Kindle Edition.
B. The time of the fulfillment of the New Covenant. It has been agreed that the time of the new covenant was future. It was always viewed as future when reference is made to it in the Old Testament prophecies. Hosea (2:18-20), Isaiah (55:3), Ezekiel (16:60, 62; 20:37; 34:25-26) all spoke of it as future. It must be viewed as yet future, for this covenant can not be realized by Israel until God has effected her salvation and restoration to the land.
Pentecost, J. Dwight. Things to Come: A Study in Biblical Eschatology (Kindle Locations 2289-2292). Zondervan. Kindle Edition.