I believe that in the future, the nations that previously “dominated” the Olympic Games will find it increasingly difficult to field athletes who are native to their own countries, but they will always be able to compensate for this with professional athletes from other parts of the world.

Yes. It is already happening in many sports and disciplines, where they are able to "buy" players to make up the teams in various ways.

I think sport is a good indicator of many parts of society, including what we are willing to support culturally. For instance, I was reading today in Finland that second generation professionals, are something like five times less likely to work in their professional field than someone who is "Finnish" (going back many generations etc). They aren't truly seen as Finns, even though born and raised here, going to the army etc. However, if one of them was a football professional instead, they would be claimed as Finnish immediately. Funny, eh?