The post by Margus (and also from others above) is the kind of informative post which matters.

He is right about the committed RTW riders. Many, I guess, did not have huge salaries, yet they overcame a host of obstacles to make that terrific journey, some lasting years. That is a real inspiration, and which encourages others to do likewise. Long may it continue.

Purchasing power seen against earnings can also change perceptions about affordability. Good link.

As for future technology making a difference, let's hope it comes sooner rather than later. For sure there will be something, and the development of ever more economical engines can be seen over the last few years, with more advances made in cars than bikes, I think. The new 'Track' Dutch diesel bike uses a Smart car engine to power it, with impressive kms per litre. But the bike is expensive at around 18,000 euros. Smaller petrol bikes of course may be increasingly used. Or Hartz style diesel powered bikes in an old frame.

I believe oil companies predict ample oil reserves yet to be exploited (the Arctic - as has been mentioned) so I guess the supply will be there. But the price will rise, and that may be a difficulty, especially as other developing countries buy it in increasing amounts. China is securing its future supplies with contracts all over the world, affecting price. So do politics and taxes. Hydrogen powered vehicles may be developed, cost unknown, not any time soon.

Big trips will surely continue as Margus suggests with the serious overlanders. And as has been pointed out, more big trips or RTWs are being made than ever before. I hope that lasts. I think the shorter distance trips will rise, as suggested to places like Albania, or destinations in S. America for N. Americans. As we (in the West) live longer than before many riders will have more time but less money when they stop work. I don't earn money any more, but I still want to bike travel to wherever I can, adjusted to my means. I've enjoyed the opinions of others here, which, as always, modify my view.