As I understand it, Lodsys, the patent holder is suing the 3rd party developers for using Lodsys' patented technology within the developers apps and to be clear, it's usage for one developer (if not all the developers) is in the in-app upgrade button.
So, if they "win" this lawsuit, wouldn't Lodsys then be able to sue every consumer that clicks on that upgrade button for using that patented technology without first setting up a licensing agreement with Lodsys? No? Ahh yes, the developer is incorporating the patented technology into their product to sell to the end-user. Ok so that's clear...
Actually it's not clear. Whether the end-users could be sued or not depends entirely on the language of the claims. If the end-user is performing the claimed method, the end-user could be sued (in such a scenario the developers would be sued for inducing the direct infringement by the end-users). If the claims are system, rather than method, claims, then the developer is "manufacturing," selling, or offering to sell the infringing system (the software), and the end-user is not performing any acts of direct infringement and could not be sued. Off hand I cannot remember if the claims of this patent are method, system, or both.
If Lodsys wins this lawsuit, wouldn't that mean a company such as Intel, could now sue every PC builder/modder who resells these custom built PCs for not contacting Intel first and establish a license for using any motherboard that uses any Intel chipset that comes soldered onto the motherboard by the motherboard manufacturer not including the CPU? It's assumed that you paid for the CPU chip directly and therefore any licensing fee is included that purchase.
Probably not. There is a principle in patent law called "exhaustion." It's a very complicated body of law but essentially the idea is that, subject to various exceptions, if the patent holder sells a device embodying the patent to customer X, the patent holder's rights with respect to that device are "exhausted." Customer X is free to sell the device to Person Y, etc. But it gets complicated if Intel sells A, B, and C devices to customer X. Only by combining A, B, and C together is Patent Z infringed. Then what happens? There are recent court decisions about this sort of stuff (Quanta Computer v. LG Electronics, TransCore v. ETC).