128GB iPhone may continue the 'every two years' rule

iPhone 5S could match the current iPad max capacity

iPhone 5S could be 128GB

The iPhone 5S is expected to keep the same dimensions as the iPhone 5, but there's a slim chance that Apple may supersize its smartphone line with a 128GB option.

A German retail chain, Media Markt, has put a placeholder for a 128GB version of the iPhone 5 into its inventory system, according to German Apple blog Macerkopf.

The screenshot of the database listing doesn't include a model number. Instead the inventory description contains a generic xxxxxxxxx.

The mystery 128GB iPhone 5 mention could also be intended for the forthcoming iPhone 5S, speculates Media Markt. That would make more sense.

iPhone 128GB listing
Either a generic XXXXXXXX listing, or Apple changed its naughty content policy

The 'every two years rule'

Apple has stuck to a pattern of doubling the iPhone storage capacity every two years.

Currently, the iPhone 5 is available in 16GB, 32GB, and 64GB. The same storage sizes were available for theiPhone 4S.

When the company introduced the iPhone 4 and iPhone 3GS, the smartphones topped out at 32GB.

The iPhone 3G and the original iPhone hit a memory ceiling at 16GB if you go all the way back to the beginning.

Continuing with this pattern, that would mean the iPhone 5S and iPhone 6 would have a maximum capacity of 128GB.

That may not happen right away, as Apple waited until earlier this year to expand the iPad 4 line with a 128GB version. It could happen mid-cycle.

We're likely to get our first chance at finding out whether or not Apple stays true to history and introduces a 128GB iPhone 5S on September 10.