No need to apologise Ceili - I could see where you were coming from but what you were saying re the 10 billion wasn't jelling for me - but I'm not a demographer either. I'm a librarian - so I looked it up. The UN released a population projection doc in 2004 that does predictions up to 2300 AD.
They agree with you - they say world pop should peak in 2075 just under 10 billion. Can't imagine the word supporting another 3 billion at current resource consumption rates, particularly with standard of living improvements in China and India - but it's not impossible. A move to renewable energy helps.
I've long thought that a move to digitisation of information and ubiquitous cloud/networking would remove a significant resource sink in terms of the production (and shipment) of personal information storage and transport mechanisms (like newspapers, books, cds, dvds, snail mail) but I'm not sure on balance that outweigh the provision of the hardware required to access the ubiquitous cloud.
Ancillary to that is the improvement in comms which makes the transport of people less important (affecting everything from global business management to telecommuting, conferences, university attendance, medical diagnosis).
If I'm right then the big issues become water and food production/distribution.