Douglas,

That was really powerful!

And I agree with you about that transition.

You had mentioned:

"The whole book of Acts is a laying out of that transition."

and also:

"So when did that transitional period/season as detailed in the book of Acts officially end? 

Or, to put the question another way, when did the time of the church age fully get locked into place?

At the 9/10/11th of Av, when the temple was destroyed in 70 ad. 

I believe the church age was fully in place at that time.  God made it very clear.  There was no doubt."

In addition, could the writing of the epistle to the Hebrews, also mark the end of that transition?

That book clearly shows the end of the sacrifices and office of the old testament priest.

And it was written before the destruction of the temple.

When Jesus was about to ascend back to heaven, the disciples showed that they were still thinking of the kingdom from a Davidic perspective:

Acts 1:6 When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel?

After all, the temple was still there, and sacrifices still offered, for the next nearly 40 years.

Acts 21:23 Do therefore this that we say to thee: We have four men which have a vow on them;

  24 Them take, and purify thyself with them, and be at charges with them, that they may shave their heads: and all may know that those things, whereof they were informed concerning thee, are nothing; but that thou thyself also walkest orderly, and keepest the law.

  26 Then Paul took the men, and the next day purifying himself with them entered into the temple, to signify the accomplishment of the days of purification, until that an offering should be offered for every one of them.

So, it seems that during those nearly 40 years, there might have been a transition.

But with the writing of the book of Hebrews, and the destruction of the temple, the transition was complete.

Now, those saved, Jew or Gentile, it is all the same.

There is no more gospel of the circumcision, or the gospel of the uncircumcision, only the gospel of grace, to whosoever.

But during that transition, there still seemed to have been some kind of distinction, e.g. Gentiles didn't need to be circumcised, or go to the temple.

Galatians 2:7 But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter;

  8 (For he that wrought effectually in Peter to the apostleship of the circumcision, the same was mighty in me toward the Gentiles:)

Again, Douglas, thank you for your study, it is very interesting.

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