If they go Tizen.....
I played around with Tizen on a Samsung phone made for the India market. Pretty much the same as Touchwiz. It was pretty solid for a low end spec phone. On Android it most likely would have lagged a lot.
Now that IS a game changer. Fold a smartphone out into a tablet, that would be a huge hit. But it's just wishful thinking until something actually gets released, or at least shown.
I think it's only a matter of several to five years before we see something of that nature. Maybe sooner. The huge question is ......Will they implement it right for it to catch on? I'm betting yes, but who really knows.