I think one option for the future is one where we have technology truly seamlessly blends into our lives. Smartphones, VR, wearables, etc are all seeking to integrate technology with our behavior, so it makes sense that we will reach a point where these functions and innovations are integrated biologically, rather than as individual entities.
Even today, people are abandoning their wallets because of services like Apple Wallet and Google Play. If everything you need is one your phone, why carry a physical copy? Google Glass aimed to remove some the friction in our lives by providing a more intimate interface, which failed commercially, but puts us on this path towards a seamless future. And IOT systems are allowing multiple machines attuned to our needs work cooperatively without our input.
I think the goal is an interface that is basically a pill that you swallow (or inject?) that contains an entire operating system (Android, IOS, you pick) and works with your thoughts and brainwaves to produce actions. Rather than tapping your phone, gazing at your Google Glass or fiddling with your Fitbit, everything is synced with you already. Your fingerprints could each by hooked up to a different bank account or buss pass, all you have to do is clearly think about calling an Uber and one will be called. Now whether this manifests as a visual interface appearing before your eyes, or as an intangible experience remains to be seen.
Obvious consequences would include backlash from people worried about privacy, and if Google is collaborating with my thoughts, can they read my mind like Big Brother? Would we be able to give up our device fixation and focus on the world around us? Will hackers be able to manipulate our experiences?
I think the role of designers will continue to behave much the same way it does today. The format will change, but many of us will still design applications, services and experiences. Designers might get to create new functions for our fingerprints, or digestibles that temporarily augment games, physical activity, media, or at least our perception of it.
There might be a longer term and evolutionary dependency created by such a future. Kind of like how human feet have become sensitive and misshapen over time due to the invention of shoes. We might reach a point where we get so used to thinking rather than doing that we lose the ability to physically solve problems.