The iPhone not only brings in the lion’s share of Apple’s (AAPL) revenue (51.4% in Q3), but it is rapidly replacing the Mac as the hub around which the rest of Apple’s product line revolves.

Apple surprised Wall Street in the June quarter. The Street was expecting less than 5% unit sales growth year over year. Apple delivered 20%, despite all the chatter about the high end smartphone market approaching saturation.

Apple may have a harder time surprising Wall Street this time.

Among the 44 analysts we’ve heard from so far — 23 professionals and 21 amateurs — the average estimate is for iPhone unit sales of 33.4 million. (Pro average: 32.7 million; indie 34.2 million.)

That’s up 24% from the same quarter last year, when a lot of buyers were holding out for the iPhone 5. But 24% would still represent the iPhone’s best quarterly growth since Dec. 2012.

The high estimate of 38 million, representing 41% growth year over year, was submitted by Mani Ghasemlou, a newcomer at the independent Braeburn Group. The low estimate of 29 million (7% growth) came from Barclay’s Ben Reitzes.

We’ll find out who was closest to the mark when Apple reports its fiscal Q4 2013 earnings next Monday, Oct. 28.

Below: The individual analyst’s estimates — pros in blue, indies in green. Thanks as always to Posts at Eventide‘s Robert Paul Leitao for pulling together the Braeburn Group numbers.