The announcement that Apple’s iPhone 4S is coming Cricket Wireless slated for later this month has set off a storm of speculation about the possibility of other prepaid carriers getting the iPhone as well. Last week saw rumors that Boost Mobile would be next, though Boost all but denied it.

Now it looks like the other prepaid wireless carrier owned by Spring – Virgin Mobile – might actually be next to get the iPhone. Citing “people familiar with the company’s plans,” the Wall Street Journal is reporting that Sprint will announce later this week that the iPhone is coming to Virgin Mobile on July 1. Details on plan pricing and whatnot are not clear at this point, but Virgin’s existing plans are comparable to those on Cricket and Boost. Odds are Virgin Mobile iPhone customers will be paying $55 per month for unlimited talk, text, and data. Like Cricket, though, Virgin is a prepaid-only carrier. That means no carrier subsidies for the iPhone itself, which means that you’ll be paying $499.99 for your phone, though the difference in handset cost is more than offset by the amount of savings on a monthly plan from one of the big three carriers – Verizon, AT&T, and Sprint.

Apple has been steadily increasing the iPhone’s presence on wireless carriers other than the big three. Over the last month they’ve brought the iPhone to several small, local carriers. Now they’re bringing the iPhone to Cricket and (presumably) Virgin (and maybe Boost). Bringing a high-end phone like the iPhone – the single best-selling smartphone in the world – to prepaid carriers is a big move. While it may not hurt the big carriers much, it definitely lends an air of legitimacy to the prepaid carriers.

A request for comment sent to Virgin Mobile has not yet been answered.