The timeline Will Fox has mapped out is very detailed and comprehensive, and is based on what seem like the most probable current trends and economic/political directions. However, large unexpected events may change the future completely.
I envisage a section of the website devoted to alternate futures, each with a different premise. They obviously cannot be anything like as complex as the main timeline; however, there are enough links and speculative articles out there to support them on a basic level. I'd be willing to compile a few of the scenarios.
Some starting points I can think of:
1) Sudden new ice age, tirggered by an unexpected climate flip (as in The Day After Tomorrow).
2) The global warming skeptics are right after all, and serious climate change simply never happens (Merlin could write that one...).
3) A GM supervirus is accidentally unleashed, wiping out >90% of the human race within a few months. Survivors form new communities, but most existing nations cease to exist.
4) A different GM virus destroys all grass species, including major grain crops: worldwide famine, mass extinction of land animals and general collapse of society. How would people and ecosystems reorganise themselves after such a disaster?
5) Aliens make open contact with humanity and transform our civilisation with new technology and culture; or subjugate us harshly and force the emergence of a global guerilla resistance.
6) An asteroid or comet collides with the Earth - not big enough to snuff us out completely, but making life very difficult for a few decades...
7) Strong telepaths/telekinetics start being born in this century, and at least some of them see themselves as a superior human caste destined to rule the World...
Would anyone else like to work on future sidelines such as these?