It's commonly quoted that the hashrate will double when the first production of ASICs are all online giving total hashrate: ~44 Thash/s
And of course the mining payout will halve to 3600BTC
Nope... It will be more like 15-20x the current hashrate
We don't know for sure what it will be yet I think it's useful to see in black and white what the rewards are under these different hashrates.
Total network hashrate (20x current): 4400 Thash/s, 3600BTC daily reward rate
Daily payout per
Thash/s: ~8BTC
Ghash/s: ~0.009BTC
Jalapeno: ~0.034BTC
SC, Avalon, et. al. : 0.42BTC
If we look at the scenario of profitability settling in the 5-10% ROI region in line with most other businesses, I still think that there will be a lot of 'casual' miners who decide to keep their 1st gen. ASIC, because hey, it's paid for and still generating coin. I think the 'casual' miners will drop off at the next hardware iteration and the business minded players will be largely the only ones buying future improved hardware.