Source: Apple

Earlier this year, Apple (AAPL -0.81%) introduced its next generation MacBook. These devices are significantly thinner and lighter than the company's popular MacBook Air computers and -- at least according to comments made by Apple executives on the company's most recent earnings call -- are seeing strong demand.

Interestingly, as MacRumors points out, it has been four months since Apple formally announced these new MacBooks and yet shipping estimates for these computers on Apple's online store still sits at a lengthy one to two weeks.

Although there are many potential explanations as to why Apple hasn't yet fixed the inventory situation with these systems, there's one that stands out as particularly compelling.

Skylake for mobile is just around the corner
Apple's current MacBook models are powered by Intel (INTC -1.60%) Core M processors based on the company's Broadwell architecture. But it shouldn't be too long before Intel begins rolling out Core M processors based on its newer Skylake processor design, which promises performance, feature, and efficiency improvements over Broadwell. 

Indeed, according to some leaked slides from website FanlessTech, Skylake-based Core M processors should deliver as much as 17% improved CPU performance, 1.4 hours additional battery life when playing back 1080p video, and 41% better performance in 3D graphics applications.

In light of these compelling improvements, Apple may want to transition its MacBook line to Skylake-based microprocessors as soon as possible. Intel CEO Brian Krzanich indicated on the company's first quarter earnings call that Skylake-based Core M processors will arrive in the second half of 2015, suggesting that Apple will update its MacBook with these processors later this year.

Why does this mean MacBook stock is tight?
Apple CEO Tim Cook is well known for having said that inventory is "fundamentally evil," and if my hypothesis that an updated Skylake-based MacBook is coming in the second half of the year is correct, it's not hard to see why supplies of this system are tight.

The MacBook is a "new" subcategory within the company's Mac lineup, so right off the bat Apple is playing a bit of a guessing game as to what proportion of its total Mac shipments will be of this new MacBook. Given Cook's view of inventory, it makes sense that Apple would be relatively conservative about how many systems the company made available initially.

After several months, Apple now has a better idea of what kind of demand that it's seeing from the new MacBook, but given that Skylake (and presumably a MacBook built around it) is just around the corner, it may not make sense to have too many of these Broadwell-based MacBooks sitting in inventory.

Supply may improve with Skylake
Since Intel's Broadwell processors were delayed due to manufacturing issues, processors based on this architecture are expected to have a shorter-than-expected lifespan in the market.

To illustrate, although Intel released its initial batch of Core M processors in the third quarter 2014, the ones that delivered enough performance for the MacBook didn't launch until the fourth quarter of 2014. This likely led to the early 2015 -- rather than late 2014 -- MacBook launch. 

But with Intel now claiming that it will launch the follow-on to Skylake, known as Kaby Lake, in the second half of 2016, the situation should be different. If Apple launches a Skylake-based MacBook in, say, October of this year, then Apple will be able to sell that MacBook for a full year before it needs to update it.

This should allow Apple to be a bit more liberal with the number of these new MacBooks that it keeps in its own inventories as well as in the channel, ultimately improving the availability of the systems.