I wonder if they'll consider creating games for Portrait play only now. I had floated this idea a few months ago (along with a few other ideas) for a possible adapter to connect to a Joycon port:
The image I used was Mario Run, which obviously wouldn't even need a special controller. But if the right game came along for portrait mode that also was more intensive than just needing the touch screen to play, then I'd hope they'd consider such an attachment, especially since now we know that games don't have to be playable in docked mode if the gameplay calls for it.