I have a basic system with a Strato C and a Compact Terra. The new video format is certainly one incentive to upgrade to a Strato K, but just as appealing to me would be the ability to use that fast 1TB of flash storage (since I have access to 2 Gbps fiber internet). With the price of flash storage these days, to pay for it and not be able to use it is definitely a disincentive to upgrade. A Strato K without storage at a lower price would also be a good solution, as mentioned by others already.
Further down-thread someone pointed out that the Strato K only has 1 Gbps Ethernet, so that pretty much defeats the idea of faster downloads to its internal flash storage. My Compact Terra Prime HDD with 2.5 Gbps Ethernet should be faster than the Strato K already.