For my write-up today on Justification and Variegated Nomism, Volume 2: The Paradoxes of Paul, I'll quote and interact with what Douglas Moo says on pages 199-200:
"A[n] issue has sparked significant discussion among a wide variety of interpreters: the apparent contradiction between Paul's claim in [Romans] 9 that only a 'remnant' of Israel would be saved (v. 27) and his claim in ch. 11 that 'all Israel' would be saved. [N.T.] Wright has pointed to just this tension as one of the advantages of his interpretation of 'all Israel' in terms of the people of God, both Jew and Gentile. Another way to resolve the tension is to dismiss any idea of a restriction in the scope of Israel in ch. 9. But the text more naturally points in just this direction. A more fruitful approach is to highlight the distinction between corporate and individual election within Paul's argument. The Old Testament and many Jewish traditions focused on the corporate election of Israel as God's people. There arose within the intertestamental period, however, in response especially to instances of widespread apostasy, a restriction of the scope of election to particular individuals within national Israel. The validity of God's election of the nation was reasserted at the same time as the identity of those who would experience that election was restricted, on various grounds, to the 'in group.' Paul follows a similar logic, asserting the continuing validity of Israel's election as a whole (9:4-5; 11:1-2, 28) but then both restricting that election to only some within Israel and expanding the election to include Gentiles. It is always the case, then, that it is the 'remnant'----those from Israel truly chosen by God----that is saved. What 11:26 affirms, in accordance with widespread Old Testament and Jewish expectation, is that what is at present a small and inconsequential remnant will grow in the last days to encompass a significantly larger number of Israelites."
The only part of this with which I agree is Moo's last sentence. I don't think that "all Israel shall be saved" in Romans 11 is referring to the church, nor do I believe that Romans 11 is saying that only a remnant of Israel will be saved, while many Israelites will not be. So how do I reconcile Roman 9:27's statement that only a remnant shall be saved, with Romans 11's statement that all Israel shall be saved? Couldn't I just say that Paul's view is that only a remnant of Jews is saved right now, but that God will expand the number of saved Jews to include all Israel in the last days? In Romans 9, Paul argues that most Jews are hardened. In Romans 11, he presents all Israel being saved as the hardening of much of Israel comes to an end.