All the characters are still alive in the future year of 2023. It is revealed that the Hetebrinks never got married, and that Ernie has been the deacon the entire time. The reverend has also led the congregation all these years, but he has plans to hand the reigns over to his son Reuben Jr. Since we know that Reuben Jr. was probably the son born at the end of the series in 1991, that means he would be 32 years old. When 'Amen' premiered in 1986, Rolly was mentioned as being 81. That means he would be 119 in the last dream. Sadly, actor Jester Hairston who portrayed Rolly passed away in 2000.
The episode begins with Thelma and the deacon commemorating the fact that it would've been his 35th anniversary to her mother. It is 1988. We can assume that in Thelma's fantasy, she and Reuben are married as soon as possible, probably still 1988 (although they don't actually get married until 1990). The second fantasy is twelve years later, and that would be 2000. Then, it is stated that the third dream scene occurs in 2023, which would be 35 years into the future from when Thelma and the deacon began to look at the old photos and reminisce.
In the first dream scene (Thelma's dream), Thelma and Reuben have just been married and are honeymooning in Hawaii. When they finally do get married in season 4, they are scheduled to go to Hawaii, but they are fog bound and instead have their honeymoon at a hotel in Philadelphia. So Thelma's fantasy does not exactly come true.
In the second dream scene (Ernie's dream), Thelma and Reuben have been married twelve years and are still residing at the Frye home. At the end of season 5, a married Thelma and Reuben are actually still living with the deacon with hopes of buying their first home.
In the third dream scene (the reverend's dream), everyone has been made to look older, except Rolly who has a bionic hair transplant. We learn that Thelma and Reuben have had ten children and there's another one on the way. Since Thelma is about 35 when she marries Reuben, that means she would be close to 70 when she's pregnant with their last kid! The Gregory offspring are all boys, and their names are Reuben Jr., Peter, Paul, Joshua, Mark, Luke, John, Abraham, Isaiah, and Matthew. On the very last episode, Thelma gives birth to the first child, and it is indeed a boy. Its name is not given, but perhaps we can assume it is Reuben Jr., like this scene indicates.