The concept doesnt seems appealing at all
Judging from the trailers it seem theres only one upside for downsizing - no need to worry about financial issues for the rest of your life.
But theres just so many disadvantages and issuse that I doubt it would get that popular like in the movie and it would probably appeal to mainly the lower income folks not those cool rich ones.
some cons on top of my head:
its irreversible(stated in the trailer) ,really big problem there.
high chance of dying, being so small you could get killed really easily , intentional or not
smaller pool of potential mate and social circle
hard to get around, seems that you are limited to the downsize city.
lack of safety, kidnapping and murder would be so easy and harder to trace