When I asked Merc a month ago about the upgraded bike I was told:

"We are going to do an upgrade on the Merc with more gears, upgraded brakes,
etc but at the moment this has been put on hold as there hasn't been any time
to go forward on it."

So maybe it will happen someday but probably not anytime soon.
Maybe they need to sell more of the current batch of 3 speeds before
they can invest in a container load of newer models.