... would we need 120x more powerful hardware in 6 months ...
The hardware
will be 10 times (not 120x but still quite an increase) more powerful, so if you want to keep your income steady, you will need a recent hardware ... do you still use your old 386 or even Pentium I (if you are old enough to ever had one of course)?
recycled/donated anything that old ages ago.. mostly Pentium4's and PentiumD's and the AthlonX2 (or whatever the equiv at the time was) lying around my garage.
hd 4870 in one of them pulling 70, a gtx480 in a cpl year old gaming rig pulling 130, and a gts250 pulling 30 in the few years-older rig addition to a cpu mining botnet I have running at night with some client computers. nothing crazy but it was getting me 0.01 per day last summer until I tried to deal with mtgox and lost my morale with btc's when I couldn't get my hands on any USD.. then tried another broker recently when the price spiked and wanted to get back into the game.
looks like you can get about 70GH/sec for about 3.5k if you buy 2 cubes full of blades chalked full of block erupter miners... at this point you need to drop long paper into a 1,200GH/sec miner or go home.