Major changes to iOS 7 coming — what will it mean for OS X 10.9?

Jony Ive’s effort to overhaul the design of the next version of iOS(s AAPL) — which is said to include fewer real-life textures throughout, along with new email and calendar apps — may be more than the iOS team can handle on its own. According to Bloomberg’s account, Apple’s rush to finish iOS 7 for a September launch has meant bringing in members from the Mac software group.

Ive is said to be making the first major design changes to iOS since its introduction in 2007. 9to5Mac reported earlier that the next version will have “very, very flat” design, which means more like Microsoft’s(s msft) Windows Metro UI than Apple’s current preference for more realistic representations of objects, with 3D, shadowing and textured effects.

As part of his new duties, Bloomberg says Ive is looking over everything, including some of the software’s core applications — Mail and Calendar — as well as “methodically reviewing new designs.”

Designers and developers on Apple’s platform have begun to move ahead with flatter designs of their own over the past year, in some cases making iOS’s preference for overly stylized apps look more dated. And competitors large and small, from Google(s GOOG) and Facebook(s FB), down to tiny two-person development shops, have innovated on the most basic apps of the iPhone and iPad. So it’s really no surprise that Apple feels the need to rethink its design approach in 2013.

But all this has meant Mac team members have “been roped in to help the mobile software group finish the job,” Bloomberg reports.

It’s not clear what will this mean for the next version of OS X: it is also expected to at least be introduced at WWDC along with iOS 7, and if it follows the pattern of the last few years, it would be on track for a mid-to-late summer launch. The last time Apple had to bring Mac team members over to help finish a version of iOS before its introduction it resulted in a delayed introduction to OS X 10.5 Leopard — the same year the original version of iOS debuted.