It just seems like this has already been tested. About a month ago difficulty went up 40% followed by 80%, and no one left.
That's because price jumped up before that dramatically, making mining very profitable all of a sudden. Difficulty followed suit and currently seems to slowly reach the "normal" level again, where it is only slightly profitable for the average miner.
As a miner myself, I know that I can expect a 100% difficulty increase about every month, and that has been the case for the past long while. But no one is leaving.
Ok but just how many further 100% difficulty increases can you accept until it's not profitable for you anymore? I doubt it will be more than 2 or 3 given current price levels.
Of course, if you also expect that prices double every month then difficulty would continue to follow but I honestly doubt that (would be a whopping 5 million USD Bitcoin by the end of next year
I just don't see the reward decrease to 25 as that big a deal. It isn't a particularly special compared to the difficulty increases miners are always faced with.
Oh but it is special in that the difficulty increase equivalent is due to Bitcoin's law and not due to the high increase in profitability for mining.
All previous difficulty increases were driven by increasing prices which suddenly increased the profitability for mining. The difficulty increase equivalent at block 210.000 will be the first to not happen because it has become more profitable for miners to mine, therefore miners will stop the mining until it becomes profitable for them again.
In fact, it is better than standard difficulty increases because it will actually make new bitcoins more rare. This might not double the price, but it will have an offsetting factor that normal difficulty increases don't have.
Maybe, but anticipated "bad" news for the market often don't affect the price because they are, well, anticipated.