[insert wishful thinking here]
Chiro you estimates usually have at least one foot in reality but this is too completely wrong analysis.
First, we just got through the whole revenue-is-not-profit arc in this thread again. Your analysis treats revenue as if it were the same as profit with a tiny disclaimer that ASICs may be able to mine longer for cheaper. Well yeah, ASICs are literally 100 times more efficient than GPUs. GPUs are 100x costlier to operate per watt, so the revenue vs profit discrepancy is much greater for GPUs than for ASICs. The bottom line is that your analysis is way off... ASIC miners can withstand a much worse difficulty to BTC price ratio because their operating costs are 100x lower.
Second, you need to account for the fact that ASICs (and realistically, also FGPAs) can not leave mining (no SHA256 alt-coin is going anywhere). ASICs in particular have one purpose in life: bitcoin mining. That's their sole purpose in life. You can't realistically expect FPGAs and ASICs to stop mining until it becomes very unprofitable for them.
Third, due to the above, GPUs represent an ever-shrinking portion of bitcoin hashing power. If you took every single GPU off bitcoin mining today, you would still have Avalon's first two ASIC batches + all existing FPGA + ??? BFL Jalapenos worth of hashing power + anyone who kept quiet and made some FPGAs and ASICs without selling them to others + ASICminer + that guy selling USB sticks of ASICs in batches of 300. That's
already the majority of the system, given that Avalon's first two batches alone represent roughly 60 TH/s, and total bitcoin system hashing power is roughly 125 TH/s right now. Avalon third batch and chip orders and BFL chip orders after that, plus AM and other shipments or internal mining. GPUs will be a very small, trivial portion of hashing power by this fall.
Fourth, there was at least one news article last summer or fall where they interviewed some big-time GPU miners who were losing thousands of dollars but kept mining anyway because they were "true believers." There are lots of GPU miners who will mine no matter what, even if it costs them. So the impact of GPU miners leaving BTC will not be as big and fast as you might think.
Fifth, you owe taxes on mining profits anyway. If you don't get caught you may be fine, if you do, you might be facing fines or if big enough, prison time with cellmate Bubba expanding your horizons in the back. Remember, your record on the blockchain is publicly visible FOREVER so if the IRS wants to trace you, it can, if you've ever used any service or exchange where you had to give out personal information. You might think it's not worth their time right now, and that is true for small-time miners for now. But computational power rises exponentially, so the time it takes to trace back to you will drop as computers get more powerful. So if you really think BTC will explode in value, that also explodes your tax liability, and if the IRS knocks on your door 10 years from now, don't be surprised.
In summary, difficulty will only go up every two weeks for as long as people keep buying FGPA/ASICs, which is already the majority of hashing power and quickly growing. You will lose a lot of GPU miners, but some will cling to mining at a loss, and GPU hashing power will be an irrelevant portion of hashing power by fall this year anyway.
The rest of your post is the old reversal of difficulty and pricing, but that isn't why bitcoin prices exploded a few months ago. As usual, price drives difficulty, not the other way around. And demand drives price. In this case, the media outlets focused the world's attention on bitcoin. In particular the Cypress bank banditry, and the rise of media exposure in China which, on a per-capita basis, was almost absent prior to 2013. When you have such big media exposure some people get excited and buy lots of btc thinking they are early adopters.
Also, you may want to look at the threads about legal issues at bitcointalk, it's pretty nasty how expensive it is to register as a money transmitter in all fifty states, then the even huger expense of actually complying with financial regulations and demanding personal information from everyone using your exchange. Currently, ZERO bitcoin exchanges are 100% compliant. Even Coinbase isn't 100% compliant and every other exchange is in deeper doo-doo than Coinbase. There's gonna be a shakeout and we're going to be left with just 1-2 bitcoin exchanges because the incredible expense of complying with financial regulations is too much for low-volume exchanges to bear.
Further, for the first time bitcoin faces serious competition: ripple. Ripple is the only other VC-backed currency and it won't be the last. Remember that bitcoin is only valuable because of its currently strong networking effect, but note that networking effects can be overcome if the network isn't that big. And bitcoin isn't that big right now relative to the entire world economy; it's trivially small. Analogous to bitcoin, look at Friendster. Friendster was the first big social network, but it never got so huge as to thwart competitors. Friendster quickly got overcome by increased competition that exploited Friendster's downsides. In the case of Friendster, it got overloaded and slow, and people moved to Myspace and then Facebook and G+. In the case of bitcoin, it got overloaded and is ALREADY incredibly slow for most commerical transactions (10 minute average per confirmation). Competitors can spring up that are faster, or more anonymous, or whatever, and they already springing up.
It's very possible that the entire btc structure crumbles because BTC will be effectively banned from most US funds, EXACTLY as I and many others had predicted more than a year ago... I identified the centralized chokepoints like mtgox, dwolla, and lo and behold, the US govt went after the chokepoints. It's still possible to dodge the chokepoints but the ease of use has gone down, and the sense of legitimacy has decreased. Add to this how much pressure FinCEN is putting on chokepoints to reduce anonymity, the IRS may get involved, and this makes bitcoin just another non-anonymous, taxable payment method, which reduces excitement and reduces demand in the currency, which keeps a lid on price. Remember, your record on the blockchain is publicly visible FOREVER.
There is plenty of risk in BTC. Do not invest more than you can afford to lose.
Lastly, note that if you believe that BTC prices will rise in the long run, it's more profitable to simply BUY the BTCs directly.
Without doing the arithmetic, it looks like the window has closed on buying GPUs for mining profit. I'll keep my GPUs running for a few more months since they're bought and paid for, and circumstances allow me to have an effective KWH rate of about $0.07. Time to look into Litecoin?
You and everyone else using GPUs, buddy. More and more bitcoin GPU mining refugees will flood into alt-coins and make them just as unprofitable as BTC. The amount of GPU power pointed at bitcoin right now is still vastly larger than the GPU power pointed at alt-coins, so once that bitcoin GPU power leaves bitcoin in earnest, expect alt-coin difficulties to explode.