While the tweet from Samsung Mobile U.K. didn't exactly give a reason for the cancellation of the update, there is speculation that the phone's outdated hardware would not allow for a smooth user experience with Android 5.0. The handset is powered by an older Exynos 5 chipset (hexa-core 1.7GHz CPU and the Mali-T624 GPU) and offers 2GB of RAM.
The main feature of the Galaxy K zoom is the 20.7MP rear camera which comes with OIS, a Xenon flash and 10x optical zoom. If you own the device, you still have a serviceable handset (even without Android 5.0) with a great rear camera.
Samsung Galaxy K zoom
source: @SamsungMobileUK via YouMobile.org