The launch of Apple’s next-generation iPhone will propel global iPhone sales to 30 million units in the calendar fourth quarter of this year, BTIG Research analyst Walter Piecyk wrote on Wednesday. BTIG had previously estimated that Apple would sell 21.5 million iPhone handsets in the fourth quarter, but in light of Apple having recently reporting sales of 20.34 million units in the fiscal third quarter, the firm’s previous estimate is almost certainly low. Piecyk also believes Apple may sell more than 10 million iPhones in the U.S. alone in the fourth quarter. AT&T, he says, could sell as many as 5 million Apple phones next quarter thanks to the iPhone 5 launch and the possible continuation of a $50 legacy iPhone model. Verizon could sell as many as 4 million iPhones in the fourth quarter, making up 45% of the carrier’s smartphone sales in the quarter; Piecyk thinks Verizon’s continued success with 4G LTE-enabled Android smartphones will drive total smartphone sales to 9 million units in the quarter. Finally, the analyst sees Sprint launching the fifth-generation iPhone this fall, and he estimates sales of 1.5 million units in the fourth quarter.