That is only if you have an asic unit working for you now at the current difficulty. Once ASIC's hit the scene in mass force, and going by the speculation of a 700TH network, the difficulty will be upwards of 100Mill.

Formula taken from bitcoin.wiki

D * 2**32 / 600

DIfficulty*2^32/600= Network hashrate

Plug in the 700TH network hashrate that some have stated will be the hashrate post ASIC


700000000000000*600=420000000000000000

420000000000000000/2^32=97788870.334625244140625(New DIfficulty)