It will be interesting to see what happens. If Turkey decides that she is not going to get into the EU, what will happen then? She could just do the trade area thing with the EU, or could swing Islamist and re-orient towards the Middle East.

Thank you for not flaming me on my Mexico comparison, which is quite a stretch to put it politely. Mexico's population is about 1/3 of the US's, so it would actually be a bigger addition than the addition of Turkey would be to Europe. It could happen! Although it would have to be one state at a time probably...

My personal opinion is that the 21st century will be a time when very large trading blocs are established. There is no particular reason why all of Canada could not be integrated into the US, for example--if they wanted it.