Do you see the huge worldwide success of Esperanto? :P It will probably be so, theorically speaking, but if I just think to the number of dialects here in Italy, and how little Italians know Italian (I let you imagine how well English is known...).

Let's try Esperanto then !! It is easier than English !!

I don't think the world has become one yet. There are still wars going on. Until then, yes it would have one main language