There is immense buzz in the market over the features, form and release date of the next generation iPhone from Apple, ahead of Apple's Worldwide Developer Conference (WWDC) that kick starts in San Francisco next Monday. Fans have kept fingers crossed as to what CEO Steve Jobs will tell them about the next generation iPhone.

There is a quick transformation taking place on the ground though -- it's the fact that Apple has been steadily ceding ground to its numerous Android OS-based rival handsets. And, according to the latest projections, this trend is going to accelerate.

Apple iPhone's growth in the U.S. market will be curtailed by the expansion of Android-based handsets, DigiTimes reported.

With more Android-based devices hitting store shelves in the second half of 2011, the Google smartphone OS will further widen its gap with iOS thanks to its more complete ecosystem the report points out.

And there's another bad prognosis from a Nielsen survey. The survey says Android devices have become the most popular smartphones in the US, and are set to leave Apple iPhones way behind. The survey also finds Google's Android operating system (OS) is the most popular among mobile operating systems.

As many as 36 percent mobile users in the US now use an Android devices, while iPhone’s share has dwindled to just 26 percent. Blackberry commands a steady 23 percent.

And what's is Apple doing about this? Will the consumer electronics giant be ever able to get on top of Android?

For that there ought to be superior features on the iPhone 5. There is already an allegation that most of the rumored iPhone 5 features are already on Android OS-based devices. iPhone fans could catch up with their Android rival in time if apple were to release its next generation iPhone, whether it is called iPhone 4 S or iPhone 5. But is there any confirmation regarding either the specs or release date?

At the same time, a slew of Android devices slated to hit market are 4G-enabled, NFC capable, with some having ultra-high resolution cameras. It looks like about ten new Android devices are going to hit deck this summer trough various networks. And there is rumored launch of many more over the next several weeks.

It is, however, pointed out that the momentum for Android has showed signs of a slowdown. But the DigiTimes research points otherwise. The arrival of the iPhone 4 on Verizon Wireless buoyed the iOS's share of the US smartphone market by nine percentage points sequentially in the first quarter of 2011, according to the report.

But the devil is in the details. However, Verizon's actual iPhone 4 sales for the quarter reached only 2.2 million units, far below industry watchers' previous estimates of 3-4 million units, the report says.

It says Android will further widen the gap with iOS in coming months thanks to the launch of more Android-based handsets.