I'm planning to buy parts to make this rig:
https://en.bitcoin.it/wiki/Mining_rig#One_ATI_5830,_Approximately_245_Mhash/s
In about a month.

In a month will I still be able to get the same overall profit as I could with that now?
I realize the difficulty is increasing which means you make less bitcoins, and therefore less money, but doesn't that also mean a relative increase in the value of each bitcoin which should even it out?