Next, you need to consider your situation. Where do you live? Do you air condition during the summer? How do your heaters run in the winter? How cheap is the electricity?
Then, you need to calculate your projected reward. There is no single way of doing this. I would suggest making your own projections about difficulty for the next periods, assuming you will buy ASIC. Estimate the block reward at 52 BTC now (50 BTC + 2 BTC tx fees), and 28 BTC after the block cut in early December.
Now, calculate your projected costs. This includes: electricity, cooling, space, repairs, hardware depreciation, and most importantly, your time. It should then be easy to see if you will break even.
Do this for each option right now (FPGA now, or ASIC later, etc.). Make sure to consider delays in getting everything ready. If you're ready to take the risk, then place your orders.