When the Bitcoin will reach its limit.
And it continued to grow, you think the price of Bitcoin will increase?
There is no limit!!
In terms of users we still are the very beginning of adoption.
In terms of scaling there won't be a limit as well, because everytime somebody will say this, others will see this as a technical challenge and find a solution.
The internet could never scale, until it does.The limits where pushed even further.The same will happen with Bitcoin.