I never understood it all looking the same, having a shared UI. The screen real-estate and input are too different to make a unified presentation. My biggest complaint about Windows 10 is that the power user on a laptop suffers for the imagined mobile user.
The funny part is, focusing on shared data and identity brings you closer to convergence than an elegant UI does.
We saw this in the leap from WinCE to the iPhone, and from tablets that were essentially laptops with the monitor facing outwards, to iOS & android tablets. Besides the hardware finally getting to the right place, designing the UI for the experience was a huge leap.
"Convergence" feels far too much like trying to compromise one to suit the other, right when we've finally learnt not to do that.
The only problem with this is that SDL X11 eats the battery.
I don't really like the one device to rule them all philosophy, a single device would be too compromised for the different use cases I have for computers, but I don't think this is a valid objection in this vision of the future.
No one has to worry if the compute core of the family room computer is available, for example- they just use the family room computer, which is its own separate device, and already affordable for nearly everyone.
Given FirefoxOS is also retired and ChromeOS seems to be in the process of being replaced by or merged with Android, I figure the cross-platform toolkits are more likely to win than the browser OSes.
Imagine, a process per browser tab for all the things! Why should this not be the case? It would be a revolutionary improvement in process visibility, in general. moreover I don't see why there would be any limitations over what you get with ps and dtrace.
Indeed, I suspect there is a quite nice visualization of the kernel itself that would fit nicely in a browser tab. Maybe not a real-time picture, but surely you could do simple simulations at the very least, and perhaps set configuration options if you wanted to change your own kernel.
React Native and NativeScript are exploring different tactics beyond the most limited webviews on Android and iOS systems. Crosswalk and others explore yet another approach for bringing better webviews to such platforms.
At some point too, performance doesn't matter so long as the users are happy. A lot of technical folks notice performance, but most consumers do not. WebView-based application toolkits don't need performance to "win", they just need that sweet spot of developer productivity and user engagement that is much easier to do than you think, with or without "performance".