The example you give is so-called primary dialects -- those that stay in place for 1000 years or more, and become very different. These are dialects in Europe,

The example you give is so-called primary dialects -- those that stay in place for 1000 years or more, and become very different. These are dialects in Europe, except for areas like Poland, where many people were displaced in WW2. There are also so-called secondary dialects. They appear where area is colonized, people from different dialects mix together, and differences disappear. But then they start developing. This is what happens in Latin America. In Russia, primary dialects are in the Western part, but east of Nizhni Novgorod they end, because Russia got those territories only after year 1500. In LA, people mostly settled 2-3 centuries ago, and differences are already big. Brasilians already can tell origins of each other by accent and vocabulary (they were puzzled by my accent and asked which state I'm from). USSR moved a lot of people across the country quite recently, and yet differences between regions appear and are developing. To test if there's oligarchy, we should probably measure whether European Portuguese is converging with Brasilian because of media and the amount of cultural content Brasilians produce. I don't know for sure, but I'd bet they don't. I saw a public person speculate that small national languages will disappear soon. But that's just not true. First phase of language dissapearance is when natives switch to another one in some areas -- like court, school or science -- and feel normal discussing school or law matters in the "colonial" language. Then it may lose more areas of use, shrink to home usage, and then be lost, because kids want to use the more socially prestigious language, rather their mother tongue. But this only happens to languages of minorities smaller than 1M speakers in bigger countries.