All true. To elaborate slightly on (4), Mars 2020, which is scheduled for launch in summer 2020, will have the ability to gather 20 samples into a sample cache

All true. To elaborate slightly on (4), Mars 2020, which is scheduled for launch in summer 2020, will have the ability to gather 20 samples into a sample cache, and drop the cache container off, for a possible future return pick-up. So, it's getting closer.