Things being priced in is a misnomer. It can be true for a snapshot in time but markets are dynamic and all it takes as we approach the Halving is for a whale to make a big buy and suddenly trigger a bullish run the entire community has been waiting for.
Let's consider the often repeated scenario of a "whale" buying or selling a large quantity of bitcoins in order to start a trend and then profit from the trend.
TL;DR: It is not realistic. It rarely, if ever, happens -- at least not on purpose.
First, in order to buy (or sell) a large quantity, the whale must accept a price that is significantly higher (or lower) than the current price. If the price does not stabilize at the new level, then the whale loses a lot of money. There is a huge risk to just break even and the typical result is the price returning the original level.
Consider the "flash crash" in the stock market a few years ago. In this case, a trader accidentally sold a huge quantity of stocks or derivatives. The price fell dramatically and the trader got a much lower price for the assets. Then, the price immediately recovered and the trader lost a huge amount of money. Note that these dumps are never on purpose. No trader would do this intentionally because the expected result is a huge loss.
Consider what happened on the Gemini Exchange last year. A trader accidentally bought a huge amount of bitcoins and the price on the exchange spiked up to $2200. The price did not stay at $2200. It immediately dropped back to the normal price and the trader would have lost most of their money if the exchange didn't roll back the trade.
Consider the Hunt brothers in the 1980s. They tried to corner the silver market by buying up all the silver. They hoped they could sell at a new higher price. They failed and lost everything.
Second, in order for whale to profit, they must unwind the trade. That is, if they bought a huge number of bitcoins, they must then sell them. If the price rose when they bought them, then it will fall when they sell them. The trader loses in both directions.
A rational trader will not attempt such a folly because the expected result is a loss.
Also, note that what I have described here is not how a "pump and dump" works. Look up "pump and dump" here:
http://www.investopedia.com/terms/p/pumpanddump.asp