We know, these rumors regarding Apple’s upcoming iPhone announcement are getting out of control. Are there going to be two different smartphone models, or just one as usual? Will it resemble its predecessor, or feature an all new design?

Another question is that if there is a low-end smartphone introduced, what will it look like? We’ve heard a lot of scenarios, but at this point a retooled iPhone 4 seems the most likely. GigaOM lends support to this theory, relaying a report from Apple’s supply chain…

The news comes from Rodman & Renshaw analyst Ashok Kumar, who’s been speaking with overseas sources about Apple’s plans for the Fall:

“From a supply chain perspective, total iPhone volumes could be up high single digits sequentially to around 22 million units with the upgraded iPhone representing almost a quarter of the volume. The “new” iPhone is expected to be a spec upgrade and not a complete redesign. It is likely that the existing iPhone 4 could be repositioned as a “lower” cost device and will continue to ship until the rollout of the completely redesigned iphone sometime next year.”

Not only is Apple expected to relaunch the iPhone 4 this Fall, but it’s expected to be its most popular model. According to Kumar, out of the 22 million iPhones Apple will make next quarter, 17 million of them will be iPhone 4s.

Apple has had a lot of success with its $49 3GS promotion, so it would make sense to do something similar with this year’s model. The question is how do they turn a $650 phone into a $300 phone?

After 14 months of making the device, Apple’s manufacturing lines for the iPhone 4 have to be running at top efficiency. And on top of production costs saved, Apple has also been rumored to be swapping out the bigger hard drives for a less expensive 8GB.

While a low-cost iPhone 4 reincarnation will surely appease investors (and sell like hotcakes), the lack of a completely revamped iPhone might turn off some would-be purchasers. I know that it’ll make the decision more difficult for me. What about you?