It’s only a tiny sample, so large conclusions must not be drawn. But the survey results reported in Gene Munster’s note to Piper Jaffray clients Monday suggest that the pent-up demand for Apple’s (AAPL) next iPhone could be even stronger than suspected.

In a survey of 216 mobile phone users conducted one recent week in Minneapolis ( in “food courts, on the street, near the entrance of a baseball stadium on a game day”), Munster found evidence that the iPhone’s market share could by his estimate double in the next round of smartphone purchases. Specifically he found:

• Among all respondents 64% indicated that they plan to buy an iPhone when they purchase a new phone.
• Of those surveyed, 29% already have iPhones and 64% expect their next phone to be an iPhone; 17% have an Android device and 17% also indicated they expect their next phone to be an Android.
• Among those who do not have an iPhone but plan to buy an iPhone next, 60% are specifically waiting for the iPhone 5
• Of those Verizon subs who do not have an iPhone but plan to buy an iPhone next, 74% are specifically waiting for the iPhone 5,
• At AT&T, that same metric is 53%.
• Among existing iPhone users, 94% expect to buy another iPhone (6% expect to switch to Android)
• Among existing Android users 47% expect to buy another Android smartphone (42% expect to switch to iPhone). [Emphasis ours.]
• Among all BlackBerry users just 26% expect to buy another BlackBerry, 67% expect to buy an iPhone and 3% expect to buy an Android device.

“In other words,” Munster concludes, “our survey suggests Apple will take share from BlackBerry and, to a lesser degree, Android as well as other smartphones and feature phones in the future. ”

Below: The spreadsheet from which the pie charts were drawn.