A phone whose screen is interrupted by a "crease" down the middle will not be an acceptable replacement for a tablet. So I'll just continue to use both a smartphone and a separate tablet, each for the jobs it does best.
Also, I understand the new Samsung device is expected to cost somewhere in the neighborhood of $2,000US. That's a lot of money to spend on any mobile device, which is going to be vulnerable to misplacing, having stolen or simply getting trashed in daily use.
Still, this looks like a good first step toward a full-size, foldable "phablet that could replace the two separate devices -- someday.