I have only bought miners from pre-orders, and all those miners gave me money. As long as you dont put your pre-order into a scam vendor, you should be ok.
And about the main topic of the thread (about Cointerra 2TH/s miner), yes, it will be profitable. Not crazy profitable as ASICs in 2013, but profitable anyway. If your TerraMiner arrives in May, dont expect to recover your investment until late 2014.
As a guideline you shouldnt buy anything older than 28nm asics (most popular 28nm asics: KNC Jupiter/Saturn or Cointerra's 1.6TH TerraminerIV).
40nm, 55nm, 110nm, 155nm might be cheap, but you will need to power those things down by the end of 2014.
Here you have some info about why mining is still profitable this year:
https://bitcointalk.org/index.php?topic=477616.0