Can anyone inform me about theorical maximum concurrents users can be connect on hAP AC device.
50 users
150 users
500 users
2000 users
When operating in 802.11 wireless mode, RouterOS conforms with the 802.11 standard, which sets a theoretical limit of 2007 clients per radio.
I think you would be safe up to 50 users. After that you probably get reduced performance 50-80 and probably useless performance at 100.
Should perhaps be looking at more industrial strength Access Points?
Or if able to use multiple wifi units for segmented areas?
http://www.novarum.com/documents/Guidelines%20for%20Large%20Scale%20Outdoor%20WiFi%202010.pdf
http://www.revolutionwifi.net/capacity-planner/
https://www.cambiumnetworks.com/products/wifi/cnpilot-e400/
Actually we have used hAP ac in the MUM events with 120-150 users connected at the same time. If users are smartphones, or people with low requirements (also, people don’t usually all download at the same time), it will be fine for around 100
as an hAP AC will max at about 600MBit thruput over the cpu, it totatlly depends on what your clients are using …
IF they all use 10MBit streaming, you will be able to handle 60 users without problems
IF your clients use less concurrent bandwidth, you can handle more users ..
Totally agree with all of the above, however the question was “theoretical maximum” 
.. And question did not specify if it is about wifi or routing performance…
Hard to believe you would get 100 simultaneous clients on 1 AP without any impact. Just keep-alive frames and their interference would eat your airtime.
On the other hand - Routing performance? Not an issue at all, exactly as @normis said
Nest, you got me on that one!!
Concur with vecernik69! (the dirty pony).
dirty pony