Baker declined to estimate the impact of Apple's decision on U.S. retailers, saying it was impossible to gauge because NPD has no insights into how much revenue the Mac App Store was generating or how customers will react to Lion.

But he said that Apple would easily make more money on Lion than it did on the predecessor, 2009's Snow Leopard.

That upgrade sold $29, but because it was a traditional DVD-based boxed product, Apple didn't bring in as much per unit as it will with Lion as a download-only title.

Two years ago, NPD said its data showed Snow Leopard had sold in its first two weeks of availability than the 2007 upgrade to Mac OS X 10.5, aka Leopard, which was priced at $129 for a single license, $149 for a five-license Family Pack.

Baker wasn't surprised that Apple will use its Mac App Store to sell Lion.