The Bitcoin Block Reward Halving Countdown site provides a useful countdown to when the reward for each block that is mined every 10 minutes goes from 25 bitcoins to 12.5 bitcoins. This occurs every 210,000 blocks, which means the halvening after that will come in another 4 years, summer of 2020.
So this is not an event that should be taken lightly. This is a World Cup, something we only see every four years and is very special. In fact, it's so special it is unprecedented. We do not even know what the effect could be on market prices of bitcoin. Will BTC/USD break all-time-highs (ATHs) due to the reduction in supply increases as a result of the reward falling? It's hard to tell.
Miners are the obvious first losers in the reward change. They will not be able to earn as much from their activities, and thus some will drop out, the difficulty will drop, and the remaining miners will demand a higher fee. Thus, we could all be paying a bit more than the standard 0.0001 btc that is used today. At $320 for BTC/USD the current transaction fees are still dust, but if price increases and the amount needed to get timely confirmation increases, it could squeeze people who are at the margin.
But is it that simple? Will price increase just because supply increases from mining will be smaller? Or will the change have some unforeseen consequences for price?
The economics of the bitcoin ecosystem will not likely be affected in any adverse ways. For one, this block reward halving has been baked into the protocol, people have known this and it's been well-built into market participants' expectations. That said, there will be media attention surrounding the event, surely. And this could generate more hype. Together with more exciting bitcoin projects and startups releasing services in 2016 could make for a bullish cocktail going forward.