Once I got the internet, I was surprised to see very little (if any) about O'Neill's vision.
Then I reaf his vision became impossible to realize (too much stress on the structure of a giant wheel when 1G was created and after all, space is about 0G and why recreate in space what we've got on Earth).

But then came the vision for Mars...

Nothing comparable to O'Neill's.

But I'm afraid a 6 months long trip to Mars is simply far too long and another propulsion technology will be needed to shorten the trip. But will the public opinion accept to launch that new technology from the ground into LEO?