I think there is a merge that is driven by technology. The ease of global travel and communication made a global economy possible. The internet made it possible for subcultures to connect at long distances and fosters subcultures (the concept of autistic culture would not exist without the internet). These things made our perception of the earth shrink.
However, I think the merge will be limited to a "stew", meaning it will stay as many separate parts that can interact with each other as never before but still remain separate. I don't think we are heading towards an ultimate merge of a One World Order sort or even a unifying culture. I don't see us heading towards a unified center. I see us heading towards an even more interlinked web of nodes which has no center.