Supplies of current-generation 15-inch Retina MacBook Pro models are getting tight, according to MacRumors, with ship times now reportedly much longer than the usual "24 hours." This, the website pointed out on Wednesday, could mean Apple (NASDAQ:AAPL) plans to update the devices to next-generation Intel (NASDAQ:INTC) processors soon.

MacRumors suggested Apple might want to pass on Intel's Broadwell processors and skip directly to Skylake for the 15-inch Retina MacBook Pro update given the chipmaker's delays in getting Broadwell out the door.

That's certainly an interesting suggestion, but I believe Apple will go ahead and update the 15-inch Retina MacBook Pro with Broadwell this year. Here's why.

Not all Skylake chips are coming at the same time
If you study Intel's historical processor release schedules, you'll see the company doesn't release all of the models of a given processor family at the same time.

For example, in the Broadwell rollout, the first parts that made it to market were the small 2+2 configuration (two CPU cores, GT2 graphics) late last year. Then, the 2+3 parts hit the market (two CPU cores, GT3 graphics). The Broadwell part that is supposed to be suitable for the 15-inch MacBook Pro, the 4+3e (four CPU cores, GT3 graphics, on-package memory), is up next.

I suspect the situation will be mirrored with Skylake. It's pretty well known that the Core M and the "traditional desktop" (as Intel refers to it) parts will launch during the second half of this year. My guess is that the more powerful chips suitable for a 15-inch Retina MacBook Pro-class machine won't be released until sometime during 2016. 

This means that if Apple wants to update the 15-inch Retina MacBook Pro soon, it will have to go with Broadwell. 

What does this mean for the 15-inch Retina MacBook Pro?
The Broadwell 4+3e chip that I expect to be inside the next MacBook Pro should be a nice upgrade from the Haswell 4+3e chip found inside the current MacBook Pro. The CPU cores are slightly improved, the graphics architecture has been enhanced, and Intel also threw in more graphics cores (48 in Broadwell 4+3e, up from 40 in Haswell 4+3e).

The move to 14-nanometer manufacturing technology from the 22-nanometer technology used to build the Haswell part should also result in better power efficiency.

As far as the system itself goes, it's widely expected that Apple will include a Force Touch trackpad on the updated 15-inch Retina MacBook Pro. Other than that, though, I don't think Apple intends to make meaningful changes to the industrial design in this round.

When will it launch?
MacRumors noted that an Intel product launch schedule that leaked last year showed that the Broadwell parts that would be appropriate for a 15-inch Retina MacBook Pro update aren't expected to launch until the July/August time frame.

This could mean an updated 15-inch Retina MacBook Pro might be quite a ways off.

However, there's some hope that Intel might deliver these big Broadwell chips before then. According to a leaked road map that has been circulating around the Web (it's also shown in the MacRumors article), Intel plans to launch the i7-5775C and i5-5675C chips for desktops during the second quarter of 2015.

These chips, to my knowledge, are based on the same silicon that would be suitable for a 15-inch Retina MacBook Pro. The second quarter ends in June, so that might mean Intel could be ready to support a 15-inch Retina MacBook Pro refresh at WWDC early that month, as some expect.