It will, just look at how much is on preorder, ASIC miner wants to have 800th to 1000th by the end of the year, thats already a 500% increase.
KNC has about 500th on preorder, BFL would have similar, there are also the 100 of thousands if not millions of Avalon chips all rated at 0.3gh soon to be shipped, then we have ActiveMining with there 24th monster machines.
A conservative estimate would put hashing power at 2ph - 4ph by January, a crazy 1000% to 2000% increase. Then your PMB's will earn next to nothing.
I kind of view the PMB's like a ponzi scheme. Those who get in at the very beginning may make ROI (between their interest and the ability to sell their shares to others via the market) but with every passing day a new person jumping in has a less and less chance of achieving ROI.
I'm still amazed some of the PMB's are being bought for prices that would take, at the current difficulty, over a year to achieve ROI. I can't fathom what people are thinking with those decisions...