Buy your bitcoins now. They will be rare soon!
And how would that be? Coins will (on average) be generated every 10 minutes and until we reach block 210,000 it will always be 50 of them. Difficulty goes up (or down) to ensure just that. Right now there are slightly more than 300 coins produced per hour, that's why the difficulty estimate is pointing upwards.
But yeah, unless you're just mining for fun or want to invest in a serious 1+ GH/s rig, don't get into mining. At least do some calculations on your own with realistic scenarios!