Other answers have covered the topic well and 2 things to clarify:
The current issuance rate is known: 5 ETH every ~15 seconds (Bitcoin is currently 25 BTC every ~10mins).
With any changes to Ethereum, such as the transition to PoS, the issuance rate is guaranteed to not increase. But it may decrease, possibly to zero or something much less than 5 ETH, when the transition to PoS happens.