Apple has officially announced the sale of unlocked iPhone 4 through its stores in the United States and the devices will be available hours from now.

Is Apple clearing the deck for the arrival of the iPhone 5? Or is it a marketing strategy aimed at international travellers who would want to insert micro-SIM card from any GSM carrier in their local countries? Or, on a broader scale, is Apple paving the way for what is dubbed as the 'global iPhone 5'?

Within the U.S. an unlocked iPhone is much less attractive now than before. A buyer of unlocked iPhone would want to use it on networks other than At&T and Verizon which already offer iPhone on their networks. It is said At&T is eying to buy T-Mobile. If it happens it would make Sprint the only carrier in the US without an iPhone on its network.

And then, there is already talk that Sprint could soon feature iPhone on its network!

Tech observers say there could be more to the launch of the unlocked iPhone 4 than what appears on the surface. Events, or non-events for that matter, related to Apple product launch decision in recent past are related to each other, rather than being coincidences or supply chain impacted decisions.

First, there was no June launch of a new iPhone. The WWDC passed by without shaking up the gadget world. In April, Apple brought in the while iPhone 4, a surprising move well into the last lap of the product cycle. And then the iOS -- Apple laid out a blueprint of what its ultimate gadgets like iPhone, iPad and iPod touch will have in future as they get into a bare-knuckle fight with Android OS-based devices. And with the launch of iCloud the tech giant sought to write the script for the post-PC world of communication.

Would Apple have announced the grand entry of iOS 5 if they positively knew the gadget to feature it -- the iPhone 5 -- would be delayed too much? Has the iPhone 5 release date got more to do with Apple's finely formulated marketing strategy than with Qualcomm chip supply disruptions in Asia?

Now Apple is selling the iPhone 4 without a contract, meaning anyone who wants to use it on other networks can use it without jailbreaking. The 16 GB version of the device will be sold for $650 irrespective of the case color. The 32 GB version, white or black, will cost $100 more.

Apart from international travellers, who are the targets? Most iPhone fans are holding out patiently for the iPhone 5 launch, especially those with iPhone 3. Is Apple trying to sell the unlocked iPhone 4 to those people and clear their stocks just in time for the iPhone 5 launch?

That’s why Apple’s move is wise; with reference to iPhone 5’s launch, says Radu Tyrsina, writing in the

The launch of the unlocked iPhone 4 is also linked up to Apple's purported plans to launch a global iPhone 5. According to rumors, the global iPhone 5 will be capable to run both on GSM and CDMA networks.

Japanese tech site MacOtakara reported that the smartphone will feature a SIM card slot “for countries except United States”.

Thus, it looks like it is fair to assume that the unlocked iPhone 4 is a harbinger of an iPhone 5 launch by Apple -- sooner rather than later!