I researched this last month and the difficulty level is much too high, the ship has pretty much sailed.
Even if you get one of the newest machines designed for Bitcoin, the waiting list is huge and it would take over six months to just break even, not even counting electricity usage.
There are people claiming that the cost of a bitcoin will go way up, but I wouldn't hold my breath on that.
These people are just interested in the sales of those new machines built for the sole purpose of mining bitcoins.
They are the ones making the real money now.