I want to buy an ASIC for me. I started to check what devices are now available on market and tried to calculate their profit...

I have assumed best case scenario for difficulty increase - 30M for next period, and then additional 5M for each consecutive period (this is tendency for few months already): next increase will be 30M, then 35M, then 40M, etc

I have compared ASICs from page http://mining.thegenesisblock.com/.
With difficulty increase described above - everything is perfect for almost any new device that comes online in late 2013 and early 2014 (except BFL, even in best case their Monarch will take two ears until ROI).

But, its not like having only one existing device of that type in the world. In reality as soon as these devices will start to appear online - difficulty increase will become huuuge comparing to current. Cointerra promises to deliver 2000TH/s in December. And now whole BTC network is only around 806 TH/s. And there are at least 3 more companies that will deliver another huge amount of TH/s in few months.

Soo, in January 2014 any currently available ASIC will become worthless, right?
I suppose there is only one option - to wait for new type of Bitcoin miners, that will be superior to ASICs?