i'm very dubious about how well this would work, considering that the primary method of reading braille and gathering the context of the dot positions require swiping fingers across the cells, not just feeling them in a stationary method. One single cell at a time would drastically lower reading comprehension and speed, Plus several contractions require a contextual grouping with adjacent cells in order to make sense. A single cell with a stationary finger is definitely not the way to go.

As /u/Marconius said, Level 2 Braille's contractions require more than one cell sometimes.

Also, some people scrub their fingers back and forth over the text when they read braille. It would be similiar to someone trying to read (visually) by having a single letter show up at a time on a screen.

There was an experimental display I saw before, I couldn't find it on Google... the display portion had three or four braille cells, and it ran left and right on a track. As you moved the display part, the braille would change to the text would be. So with only a few braille cells, it would be possible to display an entire sentence. I don't think it ever worked out, though.