[ takes out crystal ball and places on table - stares deeply into the globe ]
I am a firm believer that it will keep going up in leaps and bounds until the big players 'blink'.
For now they are just staring at each other, going tit for tat, matching hashrates to the difficulty changes. Meanwhile the cost to mine edges closer to the bitcoin rewards mined.
When the cost to mine reaches the point that there is not enough cash left over to upgrade and match the rise in difficulty, and pay bills and workers, then the difficulty rises will drop to a few percent every 14 day revolution and may even stablise.
But the new order of things will be something like the running costs being at about 85% to 90% of total mined bitcoins.
When it gets to that level, it won't change without something catastrophic happening politically, or to the tech or the network itself or the algorithm.
So if you have an Antminer S2 lets say the diff is at 65,000,000,000, BTC at $600, and its costing you about $4 USD per day to run, then you will be mining about $4.70 USD a day with your S2.
This is because the big players, eventually with their 1 PH/s racks would also be paying about $4000 USD a day ( at a guess ) to host those miners while earning a guesstimation of about $4700 USD in BTC per day.
If the value of BTC rises then large miners will afford to acquire even more miners pushing the hashrate and difficulty up and the $$$ gap between cost to mine and reward remaining about the same.
This is pretty much how the game is played everywhere else, in mining BTC it is no different. In particular its the way that China competes in business because many of their businesses can operate at thin profit margins, much thinner than anywhere else.
Eventually manufacturers in China will be the primary producers of miners, and most bitcoin will be mined there, and much of the BTC supply to the market will come out of China.
Around the world, many businesses could still run mining operations as a means of writing off profits, running their businesses at a loss and pocketing the Bitcoins themselves, however dubious that may be, that would be the only way to eventually compete, or at least, stay in the game and make something from it.
Any cartel of large mining operations in China could possibly do some damage to the world bitcoin economy if that all eventuates.
A quick look back at how OAPEC wielded supply during the Yom Kippur War is a good indicator of how supply can be used politically.
Damn near perfect analysis! The only thing I would add is the lag between 'preorder and delivery'.
Because of the extended period of time between preorder and delivery, we may actually witness the point where BTC mining becomes unprofitable for everyone. 100s of PHs could theoretically be preordered and when they are finally delivered, online and hashing, even the most efficient mining operations could be in the red.
I honestly fear that we are dangerously close to this point now. There is a LOT of hashing power coming online in the next few months. I've stopped buying new gear because of this... and also because I keep tripping breakers and my house is effing hot! Lol.