Could future technology test what lies beyond the observable universe?

[Bandersnatch]

wouldn't it be incorrect to state, for example, that the radius of the observable universe is 46 billion light-years? I say this because a comoving observer could never observe an event occurring 40 billion light-years away.

Present-time events at that comoving distance are indeed unobservable, but those having occurred there very early on - are. So there is a sense in which the statement is correct, and that sense is, I believe, the basis for how the size of the observable universe is conventionally defined.

 

[Jaime Rudas]

Present-time events at that comoving distance are indeed unobservable, but those having occurred there very early on - are.

Agreed, provided it is made clear that we are referring to comoving distance rather than proper distance.