It is a mistake to think that the more computers and devices are working in a network, the more BTC they get. This is not so. The mathematical algorithm that once was laid in the basis of the Bitcoin controls the issue of fresh coins in such a way that regardless of the number of miners and their total computing capacity a new block appears every 10 minutes.
The original reward for the found data package was 50 BTC. In 2012, the size of the reward decreased by half and currently amounts 25 BTC. The emission algorithm provides for reduction of the award by half every four years, so in the summer of 2016, the award will be reduced again to 12.5 BTC. In 2020 it will be reduced to 6.25 BTC and so on.
The total amount of bitcoins that will be issued will not exceed 21,000,000 BTC. This number is embedded in the initial algorithm and does not depend on the quantity of devices, which are mining the cryptocurrency.
But the earlier you start mining bitcoins, the more you can earn, as the amount of new coins decreases over time with diminishing rewards. The last block for which you can get the reward will be found in 2140, so it’s not too late to join to the producing of cryptocurrencies.