It has been rumors on this on Samsung camp for the past few months and finally, the Korean-based brand made it clear both in their Samsung Developers Conference and thru their official global press release
They revealed the Infinity Flex Display which you can put this future device in a small form factor and then you want more screen for various taskks, you can flap it into a 7.3 inch display. The technology was not made of glass so they need to develop a new material for the cover window that is flexible plus a unique adhesice enhances the elasticity.
To support it, they delevoped One UI with their close collaboration with Google and Android developers which will keep the bottom half of the display in use and to secure one-hand navigation plus less clutter too
Exciting times indeed for Samsung that it is not a question that we might gonna see this in a Galaxy device next year.