In a recent column, I highlighted some of the foldable and flexible smartphone display prototypes I spotted at the SID Display Conference earlier this year. These are exciting developments that could bear fruit as early as 2019. But there are some things phone makers should consider before they rush to produce dual-screen or rollable devices.

If you have a small mobile device that unfolds into two screens, for example, watching video with a seam in middle will also not be a great experience. On the other hand, vendors behind this design argue that multi-tasking features, along with a larger display, will drive demand.

If these designs make a smartphone heavier and thicker, I'm not sure how I'd feel about that, even if it means a larger display. But as I age, the need for a larger screen and bigger print grows.

The second issue is mass production. Right now, flexible display makers think they could get to mass production by 2021-2022 at the earliest, but admit there are a lot of challenges ahead. Even if they can make them in quantity, the design of any new smartphone that uses these flexible displays must be looked at holistically and that may include new types of manufacturing processes, materials, and components.

The other issue is that consumers will want and expect foldable and flexible displays in smartphones or tablets to deliver on all the benefits they've come to expect with flagship devices. That includes superior optics, durability, scratch-resistant screen covers, AR and VR capabilities, and long battery life. I don't believe they will accept any trade-offs; if anything, they'll want these new devices to surpass existing ones in terms of quality.

The foldable and flexible displays I saw at SID used screen covers made of plastic, which is highly prone to scratches and cracking and not great at optical clarity. Glass covers are superior to plastic and will be necessary to deliver the kind of rugged, quality experience consumers will expect in any next-generation mobile devices. Putting glass covers on foldable designs is easy but more challenging for flexible displays.

Ultimately, whether these gadgets hit the sweet spot of the mass market is a big question. Cost of these new form factors will also be an issue. At first, they will be priced in the premium range but will eventually get down in price so a larger audience could buy them.

Either way, these foldable and flexible displays give smartphone vendors and tablet makers a new palette of technology to work with and I expect to see many innovative designs in the future.