The church age was a complete mystery to the Old Testament believers. They did not and could not see it. They could see much prophecy fulfilled, just as we can. However, when they looked into the future, the church age was a deep valley they were unable to comprehend was even there. They could see the Millennium beyond the valley, but not the church age. Clarence Larkin in "Dispensational Truth", a highly revered scholar by many, many present day believers, describes the prophetic events that the OT believers could see as "mountain peaks".
The church age is also the pause in Daniels 70 weeks prophecy. The clock stopped ticking at the end of the 69 weeks of years, at Calvary.. The final week is still yet to come. At the radical evacuation of born again believers that happen to be alive at the end of the church age, that clock will start ticking again. Only 7 years will be left before the Millennium Reign at that point.This is the 7 year tribulation era. At its conclusion, the Millennium Reign of Jesus will begin, ruling in Jerusalem over the Great Crowd, the 144K Israelites, and all of their descendants for 1000 years.
These folks' citizenship is on the earth. Church age believers' citizenship is in heaven, but they will likely be involved on the earth in collusion with King Jesus, with "glorified" bodies like his.
After the Millennium, everyone not aligned with the enemy of God, enters eternity where the universe is rolled up like a scroll and a new heaven and a new earth is created.
This is pretty much the prevailing view of Christians today, with a few minor variations.
Much Watchtower error goes away when you do away with a 1914 invisible return of Jesus. You would think that throngs of Witnesses would wake up to the the realization that the main problem with WT theology isn't in the definition of what a "generation" is, but rather in 1914 being the date of the end of the church age.
I know the WT calls this the end of the gentile times, but it is essentially the same as the end of the church age recognized by bible-believing Christians.
We are still living in the gentile times, or the "church age" if you prefer. Heaven is still open for business. The New Covenant is still available to "whosoever will" - for the "forgiveness of sins" regardless of where the citizenship might be, ie. heaven or earth. (Mt.26: 27, 28)