In a previous post, Amos 7:1-6 and Contingent Foreknowledge, I quoted a recent work by a Catholic author, Robert Sungenis, arguing that this pericope supports contingent foreknowledge. As an Open Theist, I welcome such a conclusion, and agree that, exegetically, such is the most plausible reading.
In a recent commentary, I encountered the following about Amos 7:3 ("The Lord relented concerning this; 'it shall not be,' said the Lord") which supports this reading:
How does Yahweh react? “To repent concerning” (נחם nip’al with על) designates a change of mind prompted by the emotions, a turning away from an earlier decision on the part of someone deeply moved. From the standpoint of the party directly affected by the altered decision, the change might as easily be unfavorable as favorable. In itself, therefore, “to repent concerning” means neither forgiveness or condemnation. Here Yahwh is moved by the objection of the one to whom he has confided his intention in the vision. Just what sort of change takes place within Yahweh is more precisely defined by the quotation “It shall not happen.” In other words, the particular judgment here threatening Israel’s future—the invasion of locusts—will not be carried out. A change of mind with respect to Israel is not recognizable insofar as the forgiveness requested is not expressly granted. In fact, by 7:5 such forgiveness is no longer even requested. The terse report merely conveys that the punishment shown shall not take place. In context, this signifies initially no more than a postponement of punishment, or more precisely, a readiness to alter the sentence. If one keeps the subsequent visions in mind, one is inclined to think here, not so much of forgiveness, but rather of Yahweh offering an opportunity for selection of punishment (cf. 2 Sam 24:12ff). (Hans Walter Wolff, Joel and Amos [Hermeneia; Philadelphia: Fortress Press, 1977, 298]