50 million by end of 2019 easy.
55 million until march 3rd 2020: no way - not even close. Switch sold about 2 million units in january + february 2019.
55 million until march 31st 2020: i dont think so either, but its a close one. Switch sold about 3.3 million january until march 2019. Yes, now there is pokemon and switch lite and animal crossing on march 20th 2020, but I think It will not be enough to get to 55 million. lets say 55 million in 2nd half of april 2020. :)