Per Bloomberg's Mark Gurman, Apple (AAPL 0.42%) is planning a mild refresh of its iMac line of desktop personal computers next year. On deck are next-generation central processing units, faster graphics processors, and the addition of USB-C ports, Gurman says.

Apple's iMac lineup. Image source: Apple. 

In other words, a sensible set of upgrades and improvements, but nothing groundbreaking.

Although not much is known about the iMac computers that will follow the ones that Apple has planned for next year, there is one upgrade that could prove to be quite compelling in the 2018 iMac models -- at least to power users.

More processor cores

Since 2009, Apple's premium iMac computers have featured processors with up to four processing cores supplied by microprocessor giant Intel (INTC -2.36%). The processors Apple uses in the 2017 iMac models are likely to be Intel's seventh-generation Core processors. These chips will, just as their predecessors, also top out at four processor cores.

Of course, over the years, those processor cores have become more powerful, so performance has marched upward. However, in 2018, the desktop processor lineup that will be suitable for Apple's iMac systems, which goes by the name Coffee Lake, will feature up to six processor cores -- a 50% jump in core count from current offerings.

What this will mean to Mac buyers

An increase in core count should enable better performance in processor-intensive applications such as audio and video editing, and it should make multi-tasking smoother, especially with multiple processor intensive programs running in parallel.

The average consumer might not view more processor cores as a potential selling point, as the average consumer probably just buys a new system when his or her current system breaks or becomes too slow. However, what I think this might do is shift some prosumers or professional users away from entry-level configurations of Apple's Mac Pro, which can be configured with processors with six or more processor cores, and toward higher-end iMac models.

An iMac with a six core processors isn't going to be a suitable replacement for the Mac Pro in all use cases -- there's still a lot of stuff that Apple adds to the Mac Pro that would be tough to get into an all-in-one form factor, such as dual graphics cards. However, I suspect that for a non-trivial subset of potential Mac Pro buyers -- admittedly a small group to begin with -- the case for the Mac Pro will become tougher to make when 2018 rolls around, especially if Apple doesn't bother to update the Mac Pro soon. 

Apple will need to update the Mac Pro to keep it relevant

Apple hasn't updated the Mac Pro in years. The current Mac Pro systems use Intel's Ivy Bridge-EP processors, which first made their debut in the latter half of 2013. Since then, the chipmaker has released not one but two successors to the Ivy Bridge-EP chips, Haswell-EP and then Broadwell-EP.

The Apple Mac Pro. Image source: Apple. 

And, in mid-2017, Intel is expected to release the successor to Broadwell-EP, known as Skylake-EP.

It's not clear why Apple hasn't bothered to update this system. Perhaps Apple doesn't sell enough of them to justify the R&D investment to refresh the lineup rapidly. But if the company wants to keep this product line relevant, updating it sooner rather than later and then committing to keeping the systems fresh as new components arrive would be a good idea.