Right but while our current "laws of physics" will continue to develop what we do not know, what we do know will not change. Einstein refined rather than changed Newton. We've discovered the speed of light and what mass does when approaching the speed of light. That will not change with future discoveries.
Sure, but you are thinking that travelling at the speed of light or beyond is the only way to travel great distances. There may be technologies that we haven't even dreamt of that are being used.