I have three questions related to the July block reward halving:
1. Is it reasonable to suggest that miners' profits will be cut by about 50% with the halving?
2. As rewards for processing blocks continues to decrease, will we reach a point where only one or two of the largest mining companies will be able to profit from mining?
3. What happens when the block reward reaches zero?
1) Miner's earnings will be cut but not by 50% The exact amount depends on how may miners are turned off. As the difficulty falls the remaining miners each find more blocks. Say a 10-30% fall in the hash rate and a 20-40% fall in the income of the remaining miners. The overall impact on Bitcoin is likely to be small
2) Who knows. Don't forget miners also receive fees.
3) Ultimately miners will depend more on fees than the mining rewards.