[fivecatsandadog]

but we won't know for another 400 years, by which time it may or may not still be there, but we won't know...

The way things are going, there's a good possibility that none of our future ancestors will be around 400 years from now either.

[Verginius Rufus]

None of us will have ancestors alive 400 years from now, unless they find a way to extend lifespans to 500 years.

[SunkenCiv]

Nope, the only way to have ancestors alive in 400 years is, a la Douglas Adams, an accident with a contraceptive in a time machine. And it must have happened already whether it has happened or not, just to be confusing.