Yes, I think eventually Apple will include a memory card slot for adding more storage to their future iPhone and iPad when more of their customers and smartphone users buy a Google Android device because most Android phones has a MicroSD card Memory card slot.
But, Apple will probably use their own Memory card shape with a weird shape which only fit on Apple iPhone, and iPad. Apple will also probably sell their own Memory cards for super high prices like a 16 GB Apple Memory card will cost $100 to buy.
Apple could also release a protective case with a built-in 16GB or bigger storage drive which has a lightning port on it to connect the storage on the case to iPhone or iPad, and sell the protective case with built-in storage for $200.
Apple may listen to consumers, and shareholders who want expandable storage if Apple starts losing a lot of sales to Google Android smartphone makers like Samsung and LG which has expandable storage.
There are also more apps like YouTube which lets you save video files to view offline when you subscribe to YouTube Red. A Memory card would be useful for storing offline video files since 1080P to 4K resolution videos can use up a lot of space.
A lot of smartphone or tablets makers start trying new things when they aren't getting many buyers for their smartphones or tablets because of alternative mobiles with features which people want on their device.
Blackberry released the Priv with Google Android as its operating system which is unexpected for many Blackberry fans and users.
I think, when Tim Cook retires from Apple as CEO and other higher ranking employee retires, iOS devices may come with removable storage if the new CEO is more open to the idea of adding features like an expandable memory card slot on their iPhone and iPad devices.
Apple can also still make money selling memory cards for a higher price like how Sony makes expensive Memory Stick expandable storage cards which cost a lot more than regular SD Memory cards.
The iPad Pro is being promoted as a good tablet for professional users like graphic designers, and artists. I think there is a chance that expandable storage may come to future versions of the iPad Pro because some graphic and video files can be very large in size, and having a memory card slot would make storing, and sharing files easier with other users.
Honestly? I can't see them adding expandable memory anytime in the near future.
apple seems to hate expandable memory since it means people don't use the icloud as much and (possibly) are more likely to use their phones for longer.
Plus I don't think that they're that concerned with competing with Google devices. I mean they're a pretty distant second (with only something like 15-20% of the phone market). If anything some Android phone makers have copied apple (Samsung)... though tides have since turned and expandable memory is on the return (like with Samsung's Galaxy S7.)
Also, apply copying Sony's memory card idea would only likely anger customers. I mean one of the reasons the Vita sold poorly was because of high cost proprietary memory cards. (The Vita was like $300 by itself then had to throw another hundred on top for a memory card? You could buy a PS3, or later on... a PS4, for that much.)
Granted apple fanatics seem kind of stupid in this regard and will eagerly lap up every thing apple does... So I guess it could work.
I think many Apple users would still buy very expensive Memory Cards which only works iPhone and iPad if Apple release a version of iPhone with expandable storage. Apple release an Apple Watch, Lightning cables, and Battery case for the iPhone 6/6S, and user still buy them even when they cost a lot.
Apple can also make a special version of Apple iPhone or iPad with expandable storage, and sell the version of the iPhone with expandable storage for many hundreds of dollars more than the regular version of the iPhone without expandable storage.
but I. Rather eat them. Apple technology is damn shocking lately