by then it's not unlikely people will be pushing 500+ghash on their own with DIY asic chips.
You'd need to put in a considerable investment. Developing ASIC chips is not cheap. You'd need several million spare for development and more. I doubt BFL will let any old tom dick or harry use their IP. I'm sure there are many more companies like BFL will appear over time. It's a good thing for BitCoin companies are sinking this much in R&D. Difficulty continues to increase...
There is someone whose already developed a board for Avalon's Asics which they are releasing in batches of 10,000. You would need 10,000 to build yourself a 1.5 th/s rig... and I calculated once, the cost of that rig would be like $200,000 using the guy whose already built the board for help. At the current difficulty, that's like 60 btc/day or $6000 a day which means it would pay itself off rather quicky if you could have it now. .2 BTC a day (which I've heard is 4gh/s from another post on this topic) requires 8 GPU which you would put on 2 motherboards or around a $4000 investment + 2kw/h of power~