My opinion is Bitcoin will be between 100 US$ to 3.000$ at the end of this year.
If I should restrict the range, I would say between 300$ to 1.000$.
If USD/BTC go sideway until it touch the lower line it could be 100 around years end, but the pressure to raise would be astounding as more people use the network, new services are added and more value the network capture.
If there is a repeat of 2012 we could just go from a low 5 to an 10 high visiting 2 and 15., so we could go anywhere between 10 to 266, but I do not think so.
During 2011 the internal inflation rate of bitcoin was 4%/month to start, for a composite inflation rate of 50% YtoY, so no surprise there was a lot of pressure to lower the price (and it got the first parabolic spike).
As 2012 the inflation rate was 33% YtoY, so it explain the stable price. You have increasing adoption pushing the price up and greater inflation than the US$ pushing the price down. It managed just to grow 2x-5x (depend on when you look at it).
The current inflation rate of Bitcoin (B0) is around 10% where the current inflation of US$ (M0) is around 20% (Uncle Ben is printing 1 trillion YoY as part of QE to Infinity).
So, halving of the reward, halving the inflation rate, halving a major force pushing the price of BTC down. And this justify the spike in price, the overshooting and readjustment.
Without the halving of the reward, the price of Bitcoin would just raise as much as the users adoption (in 2013), now it can raise because it work way better than the US$ as a store of value.
In my opinion, USD/BTC is forming a bottom just now, around 100, in the worst case scenario around 90. In the absolute worst case scenario it could go to 32 now, but the rate on growth would push it to 100 by the year end. Given what we see when the price go under 100 US$, a lot of bid come out of the hood, and lower would imply a lot more buy. There is too much people hoping to buy a 50 or less that the price will never go there.
As the BTC internal inflation continue to fall from 12,5 to 11,1 next year to 10% in 2015, the advantage to hold BTC will become even more evident. (inflation is a little higher than this because blocks are mined faster than 1/600 seconds as designed but, at worst it add 1-2% inflation that will be recovered in the not so distant future). As holding Bitcoin instead of US$ (and many other currencies like € and the stuff they use in Pakistan, Brazil, Argentina and so on) become more useful, the exchange rate will raise to balance the price of the demand and the price of the demand to hold. Why keep something inflating 20% or more YtY when you can hold something inflating 10% Y2Y and reducing the rate of inflation continuously?
As people holding on bitcoin will preserve their purchasing power better than people holding US$ (or US$ denominated assets), more people will see holding bitcoin as desirable. In the same way as more argentinians owning US$ preserve their purchasing power better than argentines holding the local currency that inflate a lot faster than the US$ (sic). They do not need to understand it to believe if they can see it happen.
The fact Bitcoin is more friendly and useful to transfer purchasing power from a person to another than Credit and Debit Cards, wire and in some cases cash, gold and silver will make sure the adoption rate will continue to grow.
If the user base continue to grow 15X in two years, as in the past, we could be around 4.5 millions nodes (say people) using it in any moment of the day. The means say just 3 btc for any of them (if all BTC were spread equally). Probably there are not enough available to allow 0.3 BTC for head. If everyone wanted to have 100$ in bitcoin , a BTC would need to be, at least 300$. As people would like to save, they would keep 90% of their bitcoins and spend only the last 10% (and replenish with fiat the earn). And this would push it to 3K $ in two years.
If the user base grow faster than before or people prefer to keep more than 100$ (say 1.000$) in Bitcoin, because their fiat money is very shitty, then the price in US$ will be a lot higher.
With a 10% inflating currency you lose 65% (2/3) of your purchasing power in ten years. You are left just with 1/3 of it.
With a 20% inflating currency you lose it in 5 years (the US, for now are spreading this over all the world as the US$ is hold as a reserve currency, so in the US people feel just half of it).
Given the choice people will try to hold more of the less inflating currency available as practically possible. And this is a rational binary choice.
Who choose wisely will preserve or increase its purchasing power, who doesn't will lose it and will become irrelevant.
The adoption of Bitcoin can be very fast, so we could see the price raise a lot in response of any disturbance of the economy (and there will be a lot in the near future as this monetary system collapse)