Analysts Raise iPhone 4 Sales Forecasts From Huge to Ginormous

Overwhelming demand for Apple’s new iPhone 4 on the first day of pre-orders has sent analysts running to raise their expectations for unit sales.

In a research note this morning, Piper Jaffray’s Gene Munster increased his iPhone sales estimates for both the June and September quarters to 9.5 million from 8.5 million, arguing that Apple (AAPL) will likely sell one million iPhone 4s during the device’s first three days on the market. He also noted that the six-month extension on upgrade eligibility pricing that AT&T (T) is offering should significantly juice demand.

“AT&T has pulled forward existing iPhone users’ eligibility for upgrade pricing by up to 6 months,” Munster wrote. “In other words, all early iPhone 3GS buyers will be eligible for upgrade pricing on the iPhone 4, but last year early iPhone 3G buyers were not eligible for the iPhone 3GS upgrade pricing. Specifically, we believe that the 8.4m iPhone users activated at AT&T between the Sept-08 and Jun-09 quarters will be eligible for upgrade pricing.”

Over at UBS, analyst Maynard Um went Munster one better. “We expect the iPhone 4 launch to be larger than the iPhone 3GS launch last year which sold 1 million units in its first 3 days. Although dependent upon initial supply, we see the potential for Apple to sell 1 million units on the first day of launch.”

At this point, Um’s scenario seems the more likely. As of this writing, Apple has taken pre-orders for more than 600,000 iPhone 4s. With more than a week to go until the official launch, it’s entirely plausible that the company will hit that number. And if launch day walk-in sales are anything like they’ve been in the past, it may far exceed it.