Apple is expected Wednesday to confirm Wall Street's fears, that iPad sales growth not only slackened in the March quarter, but reversed course with fewer of the iconic tablets sold than the year before.

The Cupertino, Calif. company may have a surprise up its sleeve -- it wouldn't be the first time -- but the expectation of slowing sales has put observers, pundits and analysts on a quest for why. Why has the formerly hot-hot-hot iPad cooled off?

Some see a failure of the promise Apple implied -- or perhaps it was just customers' interpretations -- that the iPad and its app inventory could replace a traditional personal computer for many of the most popular tasks.

"I see the lull in iPad sales as a coming down to reality after unrealistic expectations, a realization that iPads aren't as ready to replace PCs as many initially hoped," Jean-Louis Gassée, a former Apple executive, wrote Sunday in his widely-read Monday Note blog. "The iPad is a tease. Its meteoric debut raised expectations that it can't currently meet."

By Wall Street's consensus, the downturn will be minor: 19.4 million iPads, or less than 1% off the same quarter in 2013. That will be a small decrease compared to the sole previous contraction, in the June quarter of last year, when sales were down 14% from the year before.

Even so, analysts are analyzing, as is their wont, and calling an ebbing of the iPad.

Some, for example, see the root of the retreat in the seasonality of sales. When Apple launches a new product, it sells boatloads in the immediate quarter of an introduction, but then watches sales slow after the initial appetite is sated.

"I think a decline in iPad sales is certainly possible, if not likely," said Sameer Singh, an analyst who covers technology -- primarily mobile -- at Tech-Thoughts, in an email reply to questions Monday. "The cyclicality of iOS products typically increases as the product line matures. With the iPhone, we've already seen sales concentrate around product launches with steeper sequential declines. I think we may see more of this with the iPad as well."

Apple rolled out its newest iPads, the 9.7-in. iPad Air and the 7.9-in. Retina-equipped iPad Mini, last October, in 2013's fourth quarter. It sold a record 26 million in those three months, 14% more than in the same stretch the year prior.

There has been, as Singh put it, a cyclicality to iPad sales, including the June 2013 quarter when numbers shrank by 14%. At the time, Apple tried to soften the downturn by pointing out that the same period in 2012 had seen the launch of new iPad models -- the third-generation, the first with Retina -- but that the corresponding one the next year had not included a launch. Instead, Apple shifted iPad debuts last year to the fall.

Ben Bajarin, an analyst at Creative Strategies, also noted, to use Singh's word, a "cyclicality" in consumer electronics, the iPad included, in the fourth quarter of the year. That's when sales, especially in the U.S., boom because of the holidays.