The Hybrid Casper upgrade is planned to take place by the end of the summer. At that point the block rewards will drop form 3 ETH per block to 0.60 ETH per block. When factoring in staking, it should be around 0.82 ETH per block based on the 5% staking interest.
This release will be a hybrid Proof of Stake and Proof of Work and is the first step until they go full Proof of Stake.
“The security of the chain is greatly shifted from PoW difficulty to PoS finality and because rewards are now issued to both validators and miners.”
EIP 1011: Hybrid Casper FFG
Once Ethereum goes full Proof of Stake, the per block rate will be as low as 0.22 ETH per block. Putting it far less inflationary than Bitcoin.
To participate in the staking, you will need 1500 ETH, or around $900,000 USD currently.
You can read the full specification here.