we need to continually increase network hash to stay ahead of the banks and their puppet regimes.
This is a misconception. Network hash rate in itself is irrelevant. What matters is the total investment in the mining business (and hobby). Based on the price of best available technology (CPUs, GPUs, FPGAs, some day ASICs) expressed in, for example, USD per GHash, this investment can be used to calculate network hashrate - but that's simply a consequence of the investment, not a relevant indicator of anything.
To rephrase your statement: total investment into mining hardware needs to grow to stay ahead of any potential adversaries. Note that the size of mining industry depends on expected ROI and the block reward plus transaction fees (expressed in bitcoins). For example, assuming a one-year ROI, it is around 1.4 million coins. This may be worth several tens of millions of US dollars.
That is what keeps Bitcoin network secure. One of many smart underpinnings of Bitcoin is that this quantifiable incentive to secure the network correlates with the value of bitcoins (size of economy), which in turn may correlate with the incentive for an established and short-sighted business to attack the network. The less valuable bitcoins are, the easier it is to attack the network, but there is less interest in doing so. The more valuable they are, the more likely they are to be perceived as a threat, but then the mining stakes are higher and it is more expensive to stage an attack via this channel.
Besides, attacking the network would really be an idiotic attempt to disrupt Bitcoin; there are much cheaper and much more effective ways to attempt this. My opinion is that
any sort of attempt by
anyone would be idiotic, as Bitcoin technology can be useful for anyone: for governments, banks, terrorists, freedom fighters, retirees, kids, travellers, non-profits - anyone. Think Internet.
Now, back to the OP - I agree that shrinking or centralization of the mining power can be a problem (simply due to random events trigerring catastrophic disruptions in small networks), but I disagree that shrinking or centralization will be happening as a consequence of ASICs.