I'd say that there already is a "splinternet", and there always has been. For example, there is the "world wide web" that is mostly http content like websites and videos. That's the largest. However, there's smaller networks that operate over the same network hardware but that are separate, such as the TOR network, Usenet, and others.

Additionally, these networks are largely already separated by language barriers. There just isn't much I can do to access say, Swedish websites or Japanese websites because I don't even know how to search for things because I don't know their language.