Few questions have been asked about how many users for particular scenario in forums never appear to be answered. So Who out there is actually using a hotspot, Whats the max number of connections you have every had on a single RB simultaneously and what RB’s did you use. Maybe someone can compile a list and then we can get an idea of maximum users per RB hotspot which will help in planning future development. 
This is a two stage answer. The first stage depends on the license level that is being used and if you are not useing a preassigned user name/password.
With a level 4 you can have 200 max users login at the same time BUT ONLY 20 if using a pay as you go system, so you get 20 paying and 180 using preassigned user name/password.
Level 5 allows 500 max users but only 50 pay as you go. So 50 paying and 450 preassigned.
Level 6 has unlimited either way. No max either way.
I have a system that had a level 5 and since I had more request for pay as you customers I up graded to level 6 and now have had no problems with 400 paying customers.
I think he is asking more about how much the RB can hadle CPU wise rather than licence max limits. And of course there is no fixed answer to this.
Regularly have 200 users on rb2011 / rb951 with circa 45% CPU
Seen 2000+ on a RB1100AH peaking around 14% CPU
These are concurrent users, not total paying customers.
Thats using lots of VLANS, bridge firewall and software buffer on the interface (slower)
I know this is an older topic, but I want to ask what your configuration is on the RB2011 to get 200 users with out maxing out at 100% CPU. We have a similar setup with 190 users on 4 different VLANs trunked in on one port. Our initial stress test ran the CPU at 100% and customers were getting slow speeds.