Apple may be scrambling to finish the next major revision of its mobile operating system in time for this summer's World Wide Developer Conference (WWDC), an annual event at which the company typically reveals new hardware and software. According to new details from Apple sleuth John Gruber of Daring Fireball, production of iOS 7 is running behind schedule and the company has reallocated engineering resources from Mac OS X 10.9 to help the mobile platform developers through the ongoing crunch.

Assuming that's accurate, the news would add credence rumors about the next version of iOS being a major overhaul. Many have criticized the platform's lack of change since launching nearly six years ago in 2007, and with former iOS VP Scott Forstall leaving the company last October, it seems like a good time for a refresh. Jony Ive, who is now the Apple-wide human interface manager, replaced Forstall and is said to be aiming for a flatter look on iOS – perhaps not unlike we've seen from Google and Microsoft.

While iOS 7 may not be ready for primetime, Gruber says it's undergoing real-world testing by staffers with carry privileges and apparently the software changes are noticeable enough that those folks are using some kind of polarizing filter on their iPhone displays. The cover is designed to reduce the screen's viewing angles and help prevent prying eyes from getting a sneak peek of what Gruber suggests is a "rather significant system-wide UI overhaul." Of course, no hard details are available just yet.

A rumor from earlier this week says that Apple CEO Tim Cook will unveil the next iPhone on June 20 at WWDC and the device will begin shipping within weeks. Based on the device's previous updates, most expect the new model to be marketed as an iPhone 5S with minor changes over today's model instead of an iPhone 6 with significant generational improvements. An underwhelming hardware upgrade could mean that Apple will rely on a greatly revamped iOS 7 to demonstrate the product line's innovation.