A linguist would probably say that Scandinavia already has a common language, and that Swedish, Norwegian and Danish are mere dialects of the same Scandinavian language. They are considered different languages mainly for political and historical reasons, but since they are mutually intelligible (with the possible exception of drunk Danes) "Scandinavian" is really a single language from a linguistic perspective.

Icelandic is a different story, of course. Thankfully, though, the Icelandic speak English rather well...