Apple is set to introduce at least one new smartphone this week, but that hasn't stopped the company from planning its next big device.

The iPhone 5S and iPhone 5C are expected to debut on Sept. 10 at a scheduled event in California. Apple is supposedly planning its next device already however, believed to be the iPhone 6, according to The Wall-Street Journal.

Smartphones being tested by Apple have ranged from 4.8 inches to as big as 6 inches, according to the report. This would be a big increase in screen size compared to the iPhone 5's 4-inch screen.

It's obvious that Apple is looking to keep up with other companies lie Samsung, which unveiled the Galaxy Note 3 recently with a 5.7-inch screen.

Apple fans will get a good idea what size the iPhone 6 will be next week once the iPhone 5S is released. The new device is expected to have a 4.7-inch screen, but Apple hasn't confirmed anything regarding the event as of press time.

An Apple spokeswoman also declined to comment to The Wall-Street Journal regarding the company testing phones with 6-inch screens.

The iPhone 5S and iPhone 5C are expected to be in stores on Sept. 20, just 10 days after being unveiled, according to a report by AppleInsider.com.

The report claims many stores have implemented vacation blackout dates from Sept. 20-22 to handle the release of the next iPhone.

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