The old covenant would have stood forever if it were complete and satisfied its stated end… i.e. if anyone could have ever been counted blameless by obedience to the law, it would have stood forever as the path to justification. First century Christian Jews wanted to retain the law, and bring Christ in alongside the law, but if you have Christ the law has no place. And if you trust in the law in any fashion, you do not have Christ. Either we believe the whole counsel of God or we do not… but you cannot cling to the old covenant in ANY of its form and still be accepted in Christ. For the Old covenant was never intended to stand forever.