[olivil]

I work in the simulation industry, and once a simulator is certified for training, you cant "update it" to another model. The customer has to buy a new 737 MAX sim. However, since the 737ng and 737 MAX are common type (meaning that in the eyes of the authorities, if you're licensed for one, you're licensed for both) customers aren't REQUIRED to get a 737 MAX sim granted that they already have a 737ng sim.

Just to clarify: you can udpate a simulator and recertifie it. e.g. in regard to the motion or visual systems etc etc. But to transform a simulator into another aircraft would be beyond economically sane.