We're just one day away from Apple's big iPhone event where the company is expected to launch new hardware. Although we won't know for sure what they'll have in store until newly appointed CEO Tim Cook takes the stage, a new leak from Vodafone Germany suggests we'll see an iPhone 4 featuring 8GB storage capacity, as well as iPhone 4S devices in 16, 32 and 64 GB sizes and both white and black variants.

The new models appeared on the accessories compatibility drop-down menus on Vodafone's website. These could simply represent best-guess placeholder entries, but the fact that the latest iTunes 10.5 beta released on Friday also contained references to an iPhone 4S suggests Apple is planning relatively small, evolutionary update for the iPhone on Tuesday rather than a completely redesigned iPhone 5 device.

The iPhone 3GS did very well in sales despite being an evolutionary update of the 3G, though Android has gained a lot of steam since then. Still, if the supposed 4S can deliver in key areas Apple still stands a good chance of luring many new buyers, or get current iPhone owners to upgrade. Previous rumors have pointed to better battery life and processing power, as well as a larger screen, while keeping the same form factor – except perhaps a slightly thinner profile.

Apple's media event for the iPhone is set for tomorrow so it won't be long until an official announcement is made.