Just, thought I'd put up some information about the difficulty increases that may occur when block 3,500,000 is reached at the beginning of April 2017.

Currently, there is a proposal submitted too Ethereum Foundation to replace difficulty increase (delay in block find times) with a tapering of block rewards (e.g. 5 ETH is reduced to 4 ETH, which is reduced again and again down to 1 ETH over time) too maintain the speed at which transactions are added to the blockchain.

April/May 2017

25seconds

1.4 months = 518,400 Eth per month

35 seconds

2.2 months = 370,285 Eth per month

55seconds

3.8 months = 235,636 Eth per month

95seconds

26 months = 136,421 Eth per month

After 2021, is when a theoretical Ice Age would begin.

Naturally, increasing difficulty and slowing block find times would reduce the speed at which transactions are added to the blockchain. However, this is all provisional on the Casper-POS being delivered towards the last quarter of 2017 or first quarter of 2018.

And, VB has hinted recently, that Casper-POS testing is going better, than previous public releases have led the markets too infer.