The ASIC era will aim to fix the 51% attack problem... or at least make it extremely costly. The farther we get into the ASIC era, the less and less likely and more costly it will be for someone to subvert the network.
1 year ago, it would have taken less than 1 million dollars to wreck the bitcoin network. 1 year from now it will take at least $100 million, if not more, assuming the price of BTC doesn't tank or something.
Granted, $100 million is pocket change for some large corporations and of course governments, so the threat is still there. But as time goes on, the cost starts to rise further and further out of reach of all but richest of entities, until it gets so costly as to be unfeasible. At that point, it's cheaper to wage a legal or physical war, but that's another problem entirely.