Does this make it 16 x 9 dimensions? Too lazy to look it up...
It's a simple calculation. Using another rumor, that fits, having a resolution of 1136x640 makes it a 4.01 inch screen (at 325.12 dpi,
that is if the current display is exactly 75x50 mm) and 99.84% the same width as exactly 16:9. So yes, I would say the point is to make it 16:9 ratio. I do welcome this and the ease of the dimensions being divisible by 16 for GPUs, and it being the same width to hold with one hand. Many apps that scroll would adapt perfectly as the top and bottom buttons can be exactly the same, just more vertical real-estate.
Watching video is obviously going to fit perfectly now.
Though using the keyboard in landscape mode will leave less above it for the display (if it has the same proportions). At least, I never use the keyboard with the phone sideways anyway. (Perhaps, landscape keyboard will be disabled all together). More likely, they keep it only 960 pixels wide,
or they allow
more keys on the screen and having exactly the same space above, vertically in landscape mode.
This keyboard being wider but not taller in landscape mode could be just like the iPad keyboard with the few extra keys. I would welcome that, but the layout would change depending on orientation and would only become unnoticeable after getting used to it. (It wouldn't be Apple's style to have a changing keyboard layout simply by changing the orientation, then again, having the current wider keys is very different anyway.)