First question, 3-4 months???
The most recent announcement from Butterfly 2 days ago says: "We are gearing up to start shipping out some dev boards and a few Jalapeno's most likely this week (at least a few dev boards) and then as more chips roll in we'll be shipping out the Jalapeno's. When the new boards land in KC, we'll start shipping Little Singles and Singles at that time. I don't currently have a time frame for those, but I should have something later this week in regards to that."
This implies we'll see singles by early May perhaps. Of course, the date always seems to slip, so I'm not holding my breath but I'd be surprised if they claimed 3-4 months at this point (for early orders at least). If you ordered now, I could see 3-4 months, but for those that ordered last summer/fall, I'd hope it would be much sooner.
Butterfly labs has about 50,000 orders presently (going by their order numbers). It's going to take them a long long time to ship that many units, so let's look at what happens if they ship just 25,000 of those:
Let's assume 70% of those are for Jalapenos (5 GH/s) and 30% are for Single SCs (50 GH/s). And let's assume 30 minirigs (1,500 GH/s) were sold.
The half-speed 25 GH/s miner didn't exist until recently.
Now, these numbers could be way off but they will give us a general idea.
Total hash power from butterfly labs would then be:
25000 (0.7) (5GHs) + 25000 (0.3) (50GHs) + 30 (1500GH/s) = 437 TH/s
The current hashrate is only about 65 TH/s currently so this will complete change mining.
That is, of course, not taking into account Avalon ASICs which will continue to arrive on the scene.
Using the bitcoin profitability calculator, with bitcoins at about $90, it will take you roughly 45 days to recoup your hardware costs, assuming that you bought a 50GH/s mining unit back when they were half the price. If you bought it more recently and spent $2500, well, first there will probably be more than 25000 units out there before they get to you, and you paid more so it will take you at least twice as long.
I think the only people who are going to do well are the people who ordered early, like within the first 10,000 orders, and that is assuming butterfly ships in the next month or two before Avalon has a change to take over.
Good Thoughts
This calculator here
http://www.bitcoinx.com/profit/ , doesn't seem to take into account that the difficulty is raising constantly ... which is a key omission.
Considering your suggestion at 437 TH/s increase in the next 6 - 7 months or so, and this chart
http://bitcoindifficulty.com/ here , then we are looking at 7x difficulty increase in that same time frame of 6 - 7 months. ( The time frame may vary depending on when butterfly ships ).
But then as devices continuing shipping, we are looking at 7x difficulty increase every, what 2 - 4 months ? ( because the difficulty increases after a set amount, irrespective of number of miners? )
Seems like a 50 GH device may get you 10 000 usd profit in the next year , if you are lucky, may be less than that. But then from the year after, the device is next to worthless. All this assuming bitcoin keeps growing in terms of devices and coverage, which I think it will, as the current bank system is going down fast.
With lower butterfly GH devices, we are looking at even less profitable margins.
I get the "long-term" prospect, I just don't like all the money shelling that is going on.