The current hash rate is 63.686 THh/s, and a production mining rig does 50 GH/s. So with a mere 1200 commercial rigs, the entire current hash rate can be duplicated.
That is why ASICs are being developed. You are comparing the network mostly of GPU/CPU to the potential hashing power of a next generation device. Once ASICs are being delivered in large quantities the network hashpower is going to grow significantly. 10x to 20x in the near future isn't that unlikely. Hashrate will probably rise by a factor of 50x and that is without further rise in exchange rate. As exchange rate rises hashpower will rise in line with it. So in 2-3 years you could be looking at more like 6,000 to 10,000 TH/s.