You're forgetting that this standard of living is not universal even within the US and Europe. There's a huge (and growing) gap between the elite and the middle class, which is itself shrinking, not to speak of the working class. More and more people are born into or fall into poverty. There are people in the US and in Europe who lead lives not recognizably different from the average citizen of what we'd consider a Third World nation. On the other hand, there are many individual CEOs that command a salary larger than the GDP of many countries.
I personally don't feel that this will ever change. In a global economy, all things being equal, I do feel that a thin veneer of prosperity will spread across the world, but there will always be a huge division between the two separate ends of the spectrum. Ultimately a country's prosperity should be judged by the size of the division. If Bill Gates were to move to Ethiopia, Ethiopia would not become one of the most prosperous countries on the face of the planet, merely by virtue of the fact that it claims as a citizen one of the most wealthy.
The problem is that in most of the world the population will grow beyond its ability to feed itself. The banner example of this, IMHO, is Egypt, a country that has a shadow of an economy dominated by its tourist industry. Much of the country is completely unlivable, and the parts that are inhabited are filled with humanity. I don't want to think about what kind of a future such a country has; it will likely continue to be heavily dependent upon foreign aid unless something drastic happens.
Another problem is the fact that, as countries move to become self-sufficient (often with the help of countries in the WENSA world), they discover that there's nothing they can do that we can't do cheaper and in greater quantity. The banner example of this is African farms. Even if African countries could feed themselves, it would still be cheaper for them to buy American produce. Thus there's really no incentive to become self-sufficient.
So, in short, there will never be a point where the globe can support 100% of the population "as we do," because the US and Europe do not support 100% of its citizens at the median standard of living. At best, as cities become linked into the global economic network, the inhabitants of those cities will attain something like life in the WENSA nations (or a reasonable facsimile thereof), but life outside of the cities will probably continue as it always has. As anyone who as visited individual cities outside of the WENSA nations can attest, this is frequently the case. Any attempt to extend a universal standard of living outside of them is unfeasible and would inevitably result in holding the dynamic centers of the economy (ie. the cities) behind.