Here is my ROI estimations (starts in 3 difficulty jumps)
http://btcinvest.net/en/bitcoin-mining-profit-calculator.php?diff=11756551917&dcosts=750&diff_mincrease=15&blpbtc=25&dhsmhs=750000&diff_mincreasedecrease=3&btcusd=650.80&dpowcon=750&btcusd_mincrease=1&pcost=0.05&calcweeks=32&dleadtime=3&action=calc
This assumes miners are being sold for $1/gh. With production costs at less than $0.8/gh there is clearly profit for the manufacturer.
Given what numbers are available most smaller miners need to be moving out of Sha256. You can hope and dream these units will be cheap but no one is going to make them if they know it is going come back and bite them when they can't sell them at the price they need to. Just a few of those those smaller board makers who would target the remaining and every dwindling small miner market.
What are your estimations based on? What numbers are available? Where are small miners moving to from sha256?
I don't see a dwindling small miner market at all. Almost every manufacturer has a small miner for sale.
I think you are also assuming that there is some next gen chips that will blow these miners out of the water which will likely not be the case for a few months (5-7 months I would guess).