What do you think humanities greatest achievement ever will be by the year 3000?
This assumes that we don’t destroy ourselves before then.
Some good examples:
Faster than light travel
Unlimited clean energy
Intelligent artificial life (AI)
Computer-human brain integration
Colony on another planet (or on another planet in another star system)
Interaction with Intelligent Alien Life (Assuming we come to them, or find them)
Holodeck (Like off ST:NG)
Worm Hole creation
Naked Singularity creation
Designing of a weapon capable of destroying the universe (Say it was built in 3001 )
Virtual Reality straight into your brain (Like the matrix)
Here’s what I think: Interdimensional/time travelling machine.
But I am sure you could come up with something better…