Components for the next-generation iPhone will start shipping at the end of May with the new smartphone to have a chance of showing up in the third quarter, according to sources from the upstream supply chain.

The new iPhone will not receive a major upgrade and may just be a slightly enhanced version of iPhone 5 (iPhone 5S), the sources said citing their latest specification data. Meanwhile, there are also rumors stating that Apple also plans to release an iPhone model using plastic chassis to push its global smartphone market share, the sources added.

With the orders, related component makers are expected to enjoy around 30% sequential growths in the second quarter. Foxconn Electronics (Hon Hai Precision Industry) chairman Terry Guo previously noted that the company's performance will start picking up after April or May. However, Foxconn declined to comment about its clients when asked about iPhone orders.

The sources pointed out that if the components are all shipped smoothly, manufacturers should be able to deliver the new iPhones to retail channels in 1-2 weeks for them to be ready to sell in the third quarter.

The iPhone 5S is expected to feature a higher-end processor as well as higher-megapixel camera modules, the sources said.

Apple is expected to ship 25-30 million iPhone 5s in the first quarter, down from 45 million units in the fourth quarter of 2012.