Acts 28 is clearly a huge event and one which is marked out in scripture as a culminating end to the book of Acts. There is no doubt in my mind that Acts 28 is hugely significant in the progress of doctrine and the spritual history of the nation of Israel and the gentiles (nations).
The question that I would like to address, though, is "When did God declare Israel to be de facto "Lo-ammi"? And when was "the mystery" of Col. 1:26 revealed in relation to Acts 28? Are these events contemporaneous?
The quotation from Isaiah 6 in Acts 28:26 follows verse 25 which says:
And when they agreed not among themselves, they departed, after that Paul had spoken one word, Well spake the Holy Ghost by Esaias the prophet unto our fathers,
Notice that Paul did not say or imply that Isaiah's statement of Israel's rebellion and spiritual blindness was fulfilled in Acts 28 but rather said:
...Well spake the Holy Ghost by Esaias the prophet unto our fathers, (Acts 28:25 KJV)
... ὅτι Καλῶς τὸ Πνεῦμα τὸ Ἅγιον ἐλάλησε διὰ Ἠσαΐου τοῦ προφήτου πρὸς τοὺς πατέρας ἡμῶν, (Acts 28:25 TBT)
The condition of Israel's leaders in Acts 28 were consistent with what Isaiah said. However, where was it de-Jure - according to legal requirements fuilfilled?
The answer is fairly clear and is found in the gospels in Matthew 13:
KJV Matthew 13:14 And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:
TBT Matthew 13:14 καὶ ἀναπληροῦται ἐπ᾽ αὐτοῖς ἡ προφητεία Ἠσαΐου, ἡ λέγουσα, Ἀκοῇ ἀκούσετε, καὶ οὐ μὴ συνῆτε· καὶ βλέποντες βλέψετε, καὶ οὐ μὴ ἴδητε.
Notice the verb used here is the strengthened form:
ἀναπληρόω fut. ἀναπληρώσω; 1aor. ἀνεπλήρωσα; (1) literally fill up, make complete; figuratively, of filling up the measure of sins sin to the limit (1TH 2.16); (2) of prophecy fulfill, confirm, cause to happen; passive be fulfilled, happen (MT 13.14);
So in Matthew 13 we find the legal ( dejure ) fulfillment of the prophecy in Isaiah 6. The question is where does it become de-facto? Where do we find the blindness, fat heart and dull ears come to fruition?
The study of Acts 29 seeks to find the biblical answers to the questions raised above. The study is multifaceted and takes us in many facinating directions.