Now I’m as tired of these next-gen iPhone rumors as the next person, but when industry-insider Jonathan Geller says he’s received iPhone information from a “solid source,” it’s hard to ignore it. Geller’s site, Boy Genius Report, has been home to several Apple exclusives in the past.

His latest report confirms that Apple will indeed be launching two different versions of the iPhone this Fall. One iPhone 4S/5 model will replace the current iPhone 4, and there will also be a cheaper model for the low-end and prepaid markets…We’ve heard from multiple sources that Apple is building this lower-end iPhone from scratch, possibly based on the iPod touch. However, Geller’s information suggests that this inexpensive device could just be the iPhone 3GS offered at a major discount.

BGR’s source claims that the iPhone 3GS will retail for no more than $350 off-contract, which is nearly 50% off it’s original full retail price. They also suggest that Apple will lower the iPhone 4 cost to make it sort of a mid-range device between the new iPhone and the discounted 3GS.

While we’ve heard this information before, this new report from BGR still introduces an interesting dynamic. If Apple does indeed launch a new iPhone 4S/5 this Fall starting at the typical $199 price tag, then lowering the iPhone 4 to $99 and also offering the 3GS for free (on-contract obviously) would give customers a full range of smartphone offerings.

And, as Geller notes, if you combine this with the fact that the iPhone is expected to be on all 4 major U.S. carriers this year (not to mention China Mobile’s network of 600 million+ users), Apple may finally have the model and carrier diversity to face Android head on.

This Fall’s anticipated iPhone event is certainly shaping up to be an interesting one. Not only is Apple expected to announce multiple versions of the iPhone, but some folks are also anticipating a new iPad model. We’re doubtful on that one, though.

All of these cheaper iPhone rumors remind us of the tip we received back in April that Apple was building two iPhone models for this Fall. Hopefully our prediction will pan out.

What do you think about all this? Does it make sense for Apple to offer the 3GS as its low-end device?