RTS plans are well advanced with many airlines that currently have grounded MAX aircraft in their fleets, these aircraft have not been mothballed but rather are in constant maintenance. My understanding is that Boeing will in effect will re deliver all grounded MAX aircraft as new in respect of warranties, this clearly can't happen overnight.
With regard to pilot training I'm unconvinced that there is an actual need for further simulator training given that for the last 18 months crews have been exposed to endless trim runways on CL & NG sims and the outcome hasn't always been successful in my observations, the prime cause being unable to quickly decide whether what they are seeing is normal STS behaviour ( including auto land pre trim nose up for a possible go around) the one comment I like from above posts is a MCAS warning light, similar to the STAB OUT OF TRIM light, crude but simple.
Having said all of the above it is unthinkable that Boeing and or operators could put the aircraft back in to service without further sim training, for to do so it would only take a matter of days before someone passed this onto the press who would have a field day.
There are more sims available now and I understand its easy enough to stick a software patch on an NG to mimic MCAS which is only software after all, talk of a minimum hours to fly the max compared to the NG is rubbish, there is very little difference in the handling of a MAX v NG (MAX is easier to fly in my experience)
How you get the public on board with the MAX will be interesting, airshows, discounted ticket prices, but the fuel burn is so much lower even Greta ought to get onboard
2020 will be an interesting year.