If you are considering a 50 then I would wait, until the 100S's start being delivered, I think there will be quite a few s/h ones around and the price will (hopefully) reflect that - but if you consider a 100S there is a trade in bonus on any FF camera plus free battery and charger promotion at the moment.
I can talk myself into the camera quite easily but its the initial (and possibly only) lens selection that I have difficulty with - the 32-64 is quite big and not super fast, the primes look great but 2-3 of them and it gets ££££, the 45-100 is another option and there is rumoured a 20-34 coming.
Also there is supposed to be a Sigma announcement today, and is today the day they launch X-mount lenses...................
Too much tech to consider....back to the X100