I was thinking about the resolution as well. That's getting really close to MBP resolutions on a much smaller screen. Plus, the PPI is probably much higher than an iMac's screen. I've heard that it's tough to scale OLED to larger screens, but still. Some other computer makers have 4K 15" laptops. For iMacs, since they're 5K now, Apple probably would want to use a 10K screen if they wanted PPI to be somewhat consistent between devices.
As for dual SIM cards, sounds interesting. Wouldn't mind a microSD as well, but not like that's going to happen. But never say never.