May I just throw in a thought...
No matter how many ideas are batted back and forth regarding how space travel will come about and who will do it (and this IS a fascinating discussion), I predict it will most likely come about in a way that we haven't considered. Too many unknowns, variables. I don't know about anyone else but I love surprises. Someone WILL have predicted the way and there will be record of it, but it will have been pooh-poohed by most knowledgeable people.