There is a significant amount of inferential distance here.

If society is changing, then those best suited to whatever society currently exists are those born relatively recently.

and

However, since 2700 hopefully will be different, the people best suited to live in it are those born in 2650, not those born in 2200.

I do not know what you mean by this. It is not obvious that, at this point in time, those individuals born relatively recently are better suited to current society than those individuals born less recently. However, I also am not sure what you mean by "better suited." Your language sounds slightly Darwinistic. However, I do not think that you are talking about fitness.