I really don't think we can expect an entirely common language any time soon. There are always regionalisms that will pop up, be adopted, and make their way into a language.

Good examples here are the words depanneur and SAQ.

A depanneur is an all-night convenience store. You know, those mom 'n pop grocerylets that sell staples (bread & milk), snack foods and cigarettes. Depanneur is French word that means "something or someone that helps you out of a bind" (like needing chips at 3:00 o'clock in the morning )

The word is a common English Québec word but would never be understood to be a convenience store anywhere else.

SAQ is the same. The only place you can buy hard liquor in Québec was at government run stores called "la Société des Alcools du Québec. Each letter is pronounced separately. So going to the Ess Aye Q is common English here but unintelligible anywhere else in Canada or the world.