Hope is generally used for something that has some decent possibility of happening. So "I hope to see you again" would basically always sound correct. Even if it's to a friend that is planning to move far away, it's not inconceivable that you wouldn't be able to see them again. With the "I hope to compete in the 2020 Olympic games" this would sound correct coming from someone who already was quite good at some sport, it would sound very odd coming from a middle aged man who hasn't played any sports since high school.
So it's not really a difference between whether you have a plan or not, it's more a difference between whether it's decently possible or not.
Also - the way I would phrase the sentiment "There is basically no chance that I am going to compete in the Olympic Games but think it would be really cool to" would probably be something like "I would love to compete in the Olympic Games" (with emphasis on "love") or something like "It would be amazing to compete in the Olympic Games". Shifting to the subjunctive there gives it a much more hypothetical feel.