New features in Android 6.0 Marshmallow could put more usefulness into the Galaxy S7's rumored SD card slot — and hurt sales of higher-capacity phones.

In a year of sweeping changes to Samsung's mobile lineup, one of the more controversial moves was the elimination of removable storage — the humble microSD slot — from the Galaxy S6 family of devices. At the time, Samsung insisted that most Galaxy owners didn't use the microSD slot, and thus wouldn't miss it. However if the rumor mill is to be believed, the company is poised to reintroduce removable storage into its anticipated 2016 flagship, the Galaxy S7.

So what does it all mean? Here are a few theories.

Adoptable storage

Engineering challenges: Adoptable versus removable storage

First up, an SD card slot in any phone running Android 6.0 Marshmallow automatically enables much more than just a way to store photos without eating into precious internal storage, or a handy way to keep your offline music cache in one place. Marhsmallow's Adoptable Storage feature lets Android use an SD card to augment your phone's internal flash, completely seamlessly.

That means apps and media will overflow onto your SD card when the internal storage is full, with no manual juggling of apps or files required.

Just because you can use an SD card to augment your internal storage, doesn't mean you should.

There are a couple of caveats: Read and write speeds won't be as fast, and thus there may be very noticeable performance dips with this feature enabled, particularly when launching apps. SD cards are fast, but they'll never be able to compare to internal storage speeds. As such, given that the GS7 is pretty much guaranteed to come with at least 32GB internal storage, you're better off using an SD card as removable storage, and manually moving stuff as needed.

The other side of the argument has to do with the physical space taken up by an SD slot. It's true that removing this extra slot, and the corresponding bits on the circuit board, saves some space in what's already a slim and compact handset. But let's be realistic here: microSD cards aren't that big, and other manufacturers like HTC and Sony have found a way to pack them into equally-skinny devices. (What's more, the engineering challenges of fitting a microSD slot into a GS6-sized smartphone pale in comparison to the work involved in bringing back the other feature that phone lacked — a fully removable battery.)

READ MORE: Inside Marshmallow's Adoptable Storage feature

The economic argument

If Samsung does include a microSD slot in the Galaxy S7, it might have a very real impact on sales of higher capacity versions of the phone. The GS6 came in 32, 64 and 128GB variants — although that was eventually whittled down to just 32 and 64GB in the S6 edge+ and Note 5.

If all Galaxy S7 models include removable storage, along with the ability to use it for just about anything, thanks to Adoptable Storage, consumers might be less inclined to stump up the extra cash for a model with extra internal storage. In turn, carriers and retailers might be less inclined to stock these more expensive options.

Samsung would prefer to sell you a more expensive 64GB GS7 upfront, rather than hoping you buy a Samsung SD card for your cheaper 32GB model.

That's to say nothing of the fact that Samsung itself would prefer to sell you a more expensive 64GB Galaxy S7 than have you buy the 32GB model and hope you pick up a Samsung SD card to use with it.

How much of an impact this has on Samsung's bottom line will depend the portion of Galaxy S7 buyers who actually care about this feature. And given that Samsung's own data showed this is a relatively small share of users (thus the removal in the GS6), maybe the effect won't be so strongly felt. Regardless, if Samsung does swing back to microSD in 2016, it'll show that removable storage remains an important feature for Android phones.

We'll likely learn more about the Galaxy S7, and the hardware lurking within in, at Mobile World Congress this February. In the meantime, what do you think about the potential return of microSD in the GS7?