The latest data from the NPD Group shows that domestic sales of Mac computers were about even year over year in the month of April, which one analyst interprets as potentially a positive sign for Apple.

Gene Munster of Piper Jaffray revealed the latest figures from NPD in a note to investors on Monday. He said the fact that Mac sales were flat year over year is a neutral to slight positive sign for Apple.

Munster's own forecast has called for total worldwide Mac sales for the June quarter to be down about 5 percent year over year.

But because the NPD group tracks domestic sales, and a greater percentage of Macs are being sold overseas, Munster noted that it's becoming increasingly difficult to draw conclusions from the NPD's monthly tracking data.

For example, in the month of March, NPD saw U.S. Mac sales down 8 percent, while Apple's official numbers revealed worldwide sales were up 7 percent for the month. The NPD data has been off by more than 10 percentage points from Apple's official worldwide numbers in three of the last five months.

In addition, Munster said Macs are becoming a "less meaningful piece of the Apple story," as the company's profits are now largely driven by the iPhone and iPad. He also expects that the iPad will continue to cannibalize Mac sales.

For the remainder of 2013, Munster sees Apple's main catalyst becoming a low-cost iPhone, which he sees being launched before the year is out. He also continues to hold out hopes that Apple will introduce a full-fledged television set.

As for its Mac lineup, Apple is expected to introduce new notebooks featuring Intel's latest Haswell processors at the company's Worldwide Developers Conference in a matter of weeks. Last week, AppleInsider noted that reseller supply of some MacBook Air models has been dwindling ahead of the anticipated product refreshes.