Okay, so I used the time shift trick to fund and build my tower to its maximum of 131 floors (ground floor, 50 residential, 16 each of the other floor types). Now I'm going through the floors and adding/moving/evicting bitizens in a quest to stock every floor with only 9-rated Dream Jobbers. I'm still restocking floors since that's one way to get more Tower Bux (you'll sometimes get a Bux for having the entire floor stocked), so the money is still coming in.
Meanwhile, the game still has the option to build additional floors. For the heck of it, since I didn't need coins for anything else (it's a pity you can't convert them back to Tower Bux, which I need), I paid around 2,500,000 coins to build floor 132. And... you can't do anything with it. If you try to make it residential or creative or whatever, the game alerts you that you've maxed out on that category.
So I've got an empty floor, and if I wanted to waste even more coins, I still have the option to build another floor.
(BTW, if you complete all 47 achievements, there's no special achievement or alert or message of congratulations or dancing bitizens - you're just done)
That kind of sucks that there is a floor limit. Thank you for the warning. It would annoy me so much seeing the empty floor just sitting there. Maybe in future updates there will be more than 16 per category. Until then, just save your coins once you hit floor 131 I'm guessing.