Even though Apple's iPhone 3GS was released only a few months ago one company in China is already claiming to have parts in stock for its successor. China Ontrade is offering what it claims is the fourth generation iPhone midboard and SIM card tray for sale on its Web site.

According to China Ontrade, it received the midboard part from Foxconn on November 1. Foxconn is one of the companies that builds products for Apple.

China Ontrade is also claiming that it has the SIM card tray for the next generation iPhone in stock. The tray is slightly larger than the current version, and the company refers to the part at "Apple iTablet iPhone 4 Generation SIM Tray," indicating that part might be destined for Apple's rumored tablet computer, too.

Apple has released new iPhone models in the July window ever since it first introduced the combination iPod and smartphone in 2007, and the iPhone 3GS has been on the market for only a few months. The possibility that the company could be prepping to release a new model now seems highly unlikely.

Building final components for a new product several months in advance doesn't seem likely, either, since those parts would have to be stockpiled until production began -- and Apple is well known for its fine-tunes just-in-time production process.

Apple recently commented that its product lineup for the holiday season is set, so the idea that a new iPhone launch will happen outside of the regular refresh cycle seems even more unlikely.

Assuming the parts are legit, Apple could be preparing to launch an iPhone that needs a different chip configuration, like CDMA instead of GSM. If so, that would lend some credibility to rumors that Apple will be signing a deal with Verizon in the United States.

[Thanks to Gizmodo for the heads up.]