Seems reasonable that this is what future sequels would cover. Let that writing happen then rather than now. One thing that the developers have never wavered on is that the first three games is Shepard's story, and it ends in ME3 (and presumably the DLC).
That's not really a reasonable assumption. Just look at DA2. It barely had any connection to the first game and didn't resolve any of the potentially significant choices you could have made in DAO. Given the underwhelming ending of ME3, why would I have any reason to assume that Bioware will properly resolve anything in future sequels?
No, we don't see what happens 20 years down the road; why, was that really necessary?
Yes? Like I said, you can make a number of significant choices in the ME series. Choices that have long-term implications. As the person making these choices, I want to know what these consequences are.