I really don't get what you're saying. Whether there ends up being 3 big miners, 1 big miner, or even zero.. How does the number of miners effect bit coins usefulness or value as a currency?
The *part* of his point that's valid, and that you're missing, is that the power to control the future flow of coins is represented in the ability to monopolize their generation - it's the problem we have now with fiats - when the central (criminal) bankers own the printing press, then the rest of us have to wait to see how many they make to know which direction the long-term value will go...
On that worry, he's got a point about the centralization of creation of *any* store of value.
BTC is not at risk for this, though. The OP misses that BTC mining is (always will be?) competitive. If ASICMiner takes their farms off-line, or even stops adding to their hashrate, there's an entire planet of other miners still running. This doesn't happen with traditional, centrally-controlled fiat currencies (under penalty of jail, i.e. counterfeiting). THE central authority dictates value (interest rates, minimum wages, tax floors) AND creates the medium of exchange - this is racketeering at it's best.
What the OP is worried about won't happen because one company goes faster than everyone else for a little while.
The part you are missing is that the production of bitcoins is already defined. Half of all the bitcoins that will ever be produced are already in circulation. The amount of bitcoins that any group (or single individual) can mine is limited. While it has some bearing on the worth of all of the coins available, no one can ever monopolize or control it. They cannot increase the amount that will be produced over specified time, and they cannot control the coins that are already out there.
Of course, this is all moot, because the idea of a few miners controlling the mining is insane. Unless someone comes up with such an insanely efficient way to mine bitcoins that it increased the difficulty 100x overnight, which is around what it would take to make Avalon ASICs stop being cost effective at current BtC rates and electricity costs in the developed world, then there will always be many, many other people mining.
The bitcoin system really is quite beautiful. The kind of leap it would take to break it would also change the world as we know it. True quantum computing may be able to do it...but that isn't even a sure thing.