I hope the tri—fold format catches on (Huawei mate xt 1&2, Samsung z trifold). If I’m going to carry around an insanely fragile and expensive device I want to maximise screen area and aspect ratio.
I had written off dual screen when the square layouts were the norm, but I think Apple has struck a good balance here between screen size and price+chunkiness+serviceability. I won’t be holding my breath for an iPhone Trio. (Not to be confused with Palm Treo.)