Devices are changing very quickly and there is no plateau in sight. This means that the owners(*) of the Vivaldi should be seen as a pioneers: it is not luxurious to be a pioneer, but if you stick with it your situation will improve and you will enjoy freedom and control all the way.
Make Play Live is not the only effort for creating an open device. Since the manufacturing numbers of the Vivaldi are so low, it would be good to have the ability to install KDE/MPL on other devices too. Other efforts that aim at hardware with customizable software are CyanogenMod and Firefox OS. CyanogenMod wants to install custom software on mass manufactured devices and Mozilla has hardware and network partners to develop devices for Firefox OS.
Collaboration on the kernel level between these three projects would be very welcome. By having a kernel that is able to boot on many devices, it will be much easier to find more people that can KDE, Firefox OS, CyanogenMod, or even Tizen on their device.
(*) an open device like the Vivali would be really owned by the person that uses it in contrast to e.g. an iPad that is never truly under the control of that person.