The AT&T (NYSE: T) stranglehold on Apple (Nasdaq: AAPL) iPhone users is about to end. In other news of the apocalypse, keep an eye out for four mysterious horsemen, three unbroken winters, and the sudden appearance of dwarf planet Nibiru.

All right, so maybe it's not a sign of the end if Apple ends its AT&T exclusivity in the U.S. market. After all, the iPhone is available from multiple carriers in other markets such as France, Sweden, and Australia -- and the multicarrier approach appears to boost the iPhone's market shares in those countries. This American strategy shift is long overdue, in my opinion. Maybe Steve Jobs simply wanted to cement the cut-rate data plan for the soon-to-launch iPad before dropping this bombshell on AT&T?

According to The Wall Street Journal, Apple is working up an iPhone model that's compatible with the wireless 3G standards deployed by Sprint Nextel (NYSE: S) and Verizon Wireless, a joint venture between Verizon (NYSE: VZ) and Vodafone (NYSE: VOD). Of those two options, the Verizon network would make more sense because it already reaches more than 90 million customers and broadens the iPhone's reach considerably.

Don't discount the Vodafone component, either. That multinational giant already sells iPhones in many markets worldwide, so there's a working relationship in place already.

There is also an outside chance that the next iPhone model might move to LTE 4G technology. That would be another way to hook up with Verizon, which is rolling out a 4G network in a generous handful of U.S. markets this year, with a wider reach planned for 2011. The rumor mill is sending mixed messages about both LTE iPhones and new models that could accommodate Verizon's 3G network standards, so nothing is set in stone yet on that point.

Offloading a few million iPhone users to Verizon would lighten the load on AT&T's overburdened data network while putting Verizon's to a whole new test. Verizon's current crop of smartphones from Research In Motion (Nasdaq: RIMM) and multiple Google (Nasdaq: GOOG) Android partners have yet to seriously challenge Verizon's data capacity. Though the iPhone represents most of AT&T's growth opportunity today, introducing Verizon into the mix might be paradoxically good for AT&T.

Fool contributor Anders Bylund owns shares in Google, but he holds no other position in any of the companies discussed here. You cannot convince him that the world will end in 2012. Sprint Nextel is a Motley Fool Inside Value pick. Google is a Motley Fool Rule Breakers selection. Apple is a Motley Fool Stock Advisor recommendation. Try any of our Foolish newsletter services free for 30 days. You can check out Anders' holdings and a concise bio if you like, and The Motley Fool is investors writing for investors.