Having only seen the pics, here are my thoughts and impressions. Hopefully the guns aren't vaporware and we'll be able to handle them in 3 weeks. All available evidence suggests to me that Glock has decided to go to a modular concept in the Gen 5 guns, which include the G43, G43x, G48, G17, G19, G19x, G34 and G45. In the each of the categories, single stack and double stack, they have 2 frame sizes and 2 (or 3 in the double stack) slides. They each have a short frame, 6rds (G43) and 15 (G19); and a long frame, 10rds (G43x, G48); 17rds (G17, G19x, G34, G45). The key difference from earlier generations is the shorter dust cover on the frame and the extended recoil spring area on the longer slides. I realize this is conjecture for the doublestack group of guns, but it is only a slight extrapolation from the smaller guns. We'll see if I'm right.
If my design philosophy is right, it answers the question about the lack of an accessory rail on the G43x and G48. I THINK, I don't know, that Glock decided keeping to the frame flexibility between sizes was more important than having two different 10rd frames. Which is why I think the G45 frame is really the new G17, G34 frame as well.
The G43 doesn't fit my hand. I don't like long frames and short slides/barrels, so the G43x doesn't appeal to me either. But the G48 does, assuming it feels good. And if it does, and I get one, I'll probably put a TLR6 on it from the get go. I picked up a couple of the Olight mini-Valkyries when they were on sale and they sit on my M&P Compact and G19. I've already gotten one holster for the M&P/light and I'm still shopping for a G19/light compatible one too. They've finally gotten the output on the small lights up high enough you can have a light without increasing the footprint at all, for which I am VERY happy!