Apple Inc. (NASDAQ:AAPL) is expected to report a 5 percent year-over-year decline in Mac sales, says Piper Jaffray analyst Gene Munster. The ‘Apple Guru’ notes that Mac sales track flat through the first two months of NPD sales data in the June quarter. The Tim Cook-led company reported a 2 percent Y-o-Y decline in Mac sales in the March quarter (compared to Munster’s estimate of 5 percent decline).

However, he said that actual sales could be a bit higher as NPD data has increasingly become difficult to use for predicting Mac sales. He sees the data as neutral to slightly positive. Mac has now become less meaningful to Apple Inc. (NASDAQ:AAPL) story. The difference between NPD data and actual Mac sales (table below) have made it extremely difficult to draw conclusions, says the Piper Jaffray analyst.

Apple Mac

iPads Eating Into Mac Sales

He says the recent supply issues with revamped Macs have also affected the reported numbers over the past few quarters. A big hurdle for Macs is another Apple Inc. (NASDAQ:AAPL) product: iPads. Munster says iPads will continue to cannibalize Macs in the coming years. Macs currently generate about 15 percent of Apple Inc. (NASDAQ:AAPL)’s total revenues.

Below is the Piper Jaffray’s revenue and earnings estimate for Apple Inc. (NASDAQ:AAPL) over the coming quarters.

Apple Revenue

Apple Earnings

Meanwhile, iPod NPD data shows a 32 percent Y-o-Y decline through May in the current quarter. Gene Munster expects iPod sales to fall 23 percent in the June quarter compared to the same period a year ago. The iPods generate about 2 percent of the Cupertino, California-based company.

Munster Still Bullish on Apple

Additionally, Piper Jaffray believes that the biggest question before Apple Inc. (NASDAQ:AAPL) is how it can boost iPhone sales growth. Munster says Apple Inc. (NASDAQ:AAPL) may launch the cheaper iPhone in the second half of this year, and a TV announcement in December. He believes that the new product launches will help the stock. Munster is optimistic about iOS 7, which he says can be a game changer.

Piper Jaffray has an Overweight rating on the stock with $655 price target. Apple Inc. (NASDAQ:AAPL) was down 0.29 percent to $401.36 at 11:06 AM EDT.