Morgan Stanley has seen the future and it’s a well-heeled Chinese man (or woman) with an iPhone.

In a note to clients Sunday, Katy Huberty drew on Morgan Stanley’s proprietary AlphaWise survey of buying patterns among China’s rapidly growing middle class to paint a picture of the smartphone market on the mainland after Apple (AAPL), as widely expected, finally signs deals with China Mobile (CHL) and China Telecom (CHA).

She assumes:

• That there are roughly 150 million high-end subscribers in China currently paying at least RMB 100 ($16) per month for mobile phone service.
• That China Unicom (CHU), currently Apple’s only official carrier, has 15 million of those subscribers, or roughly 10%.
• That late this year or early next, Apple will begin selling next-generation iPhones through China Mobile (120 million high-end subscribers) and China Telecom (15 million).
• That because 20% of China Unicom’s high-end subscribers buy iPhones, the other two carriers’ subscribers will follow suit. (8% China Mobile’s high-end customers already use iPhones, even though they get only 2G service.)
• Assuming 20% penetration, Apple should see, at a minimum, 24 million addition iPhone sales in 2013, adding $6.5o per share to the company’s bottom line.
• As the iPhone catches on and the middle class expands, that number could grow to nearly 40 million next year, adding $10 to Apple’s earnings per share.
• Eventually, says Huberty, the iPhone in China will reach penetration levels comparable to those of AT&T (T), where 63% of smartphone customers currently choose iPhones.
• In Morgan Stanley’s bull case scenario, Apple within a couple of years will be selling an additional 57 million iPhones per year in China alone.

To put that in perspective, Apple sold 68.5 million iPhones worldwide in fiscal 2011, although with the launch of the iPhone 4S in October it sold more than half that many (37 million) in just one quarter.

Below: Part of the crowd that showed up at one of Apple’s Beijing stores for the launch of the iPhone 4S.