You'll be able to hire ARRI Amiras as soon as they're available, and meanwhile, there's an amazing offer on the 4K Sony F55
Confusing news about demand for 4K: UK-based ProCam has a special offer on Sony F55s: £400/$600 per day for a complete kit (Sony 7" OLED monitor, TLS Matte Box. Zeiss CP 70-200mm lens and Zeiss CP 15.5-45mm lens, Arri FF2 Follow Focus, Sony OLED Viewfinder, MCS Moose Bars, PMW F55 + Shoulder rig)
Meanwhile, they've ordered six of the new - and specifically not 4K - ARRI Amiras.
Make of that what you will.
Actually, we don't think it means anything specifically about 4K. It's just that 4K is becoming, if not commoditised, easier to work with, and there is certainly a lot more 4K kit about.
Meanwhile, people still love the dynamic range and the highlight-handling of the still stubbornly 2K ARRI cameras. It's reasonable to expect that if the Amira is significantly lower in price than the Alexa, it's going to be very popular.