By the time.... I'll have gotten/I'll get.

[jutfrank]

It's more of a question of what it doesn't mean.

The version starting I'll get ... lacks the retrospective aspect that I'll have gotten ... has. This is an aspect that looks back from the point in future time to see completed actions. This is exactly what it seems to me you mean to do with this sentence.

 

[Ashraful Haque]

It's more of a question of what it doesn't mean.

The version starting I'll get ... lacks the retrospective aspect that I'll have gotten ... has. This is an aspect that looks back from the point in future time to see completed actions. This is exactly what it seems to me you mean to do with this sentence.

Doesn't 'I'll have gotten/get....' does that same thing? Look back from the point in future?
Someone asked me if I'll be home at 8 p.m. I said:
"I'll have finished work by the time you get here."

 

[jutfrank]

Doesn't 'I'll have gotten/get....' does that same thing? Look back from the point in future?

I'll have gotten does but I'll get doesn't. That's my point.

Someone asked me if I'll be home at 8 p.m. I said:
"I'll have finished work by the time you get here."

Yes, that's good.

But you don't really need to be retrospective in this case. It would be simpler to say I'll be home at 8.

 

[Charlie Bernstein]

I'll have gotten does but I'll get doesn't. That's my point. . . .

Yup. I'd just say, "I'll have my . . . ."