According to DigiTimes that next-generation of iPhone which they claimed it will be iPhone 4S, won't have LTE capability and its production will start by August.
What is LTE :
Long Term Evolution (LTE), is the latest standard in the mobile network technology tree
Why iPhone 4S won't have LTE:
Initially, iPhone 4S was planned to be LTE capable, but due to problems that faced Qualcomm recently in producing the chips in large enough quantities for iPhone.
Instead, LTE capability will likely make its way into the following (sixth generation) iPhone in 2012. A number of carriers, including three top Chinese telecommunication companies will be disappointed after expressing interest in selling an LTE capable iPhone. Despite this, China Mobile, which will have 27 million users by the end of this year, is expected to reach an agreement with Apple to sell the iPhone 4S when it is expected to launch in September this year.[via MacStories]