This makes sense as a unifying strategy. It's a strategy that Nvidia has adopted a while back ("we makes chips for phones-to-supercomputers"), and I think it's also a strategy Google could adopt with Android, although they first need to solve a very big problem, and that is how do you scale user interfaces for all these devices?
This is something Canonical has to think about, too. And it's not just a problem for the OS itself - finding the right user interfaces for the OS for different devices, but also getting 3rd party developers to do the same, too. I've tried different Linux distributions for years, but I quickly gave up on using them, because I couldn't stand how ugly most applications were. If I, as a pretty technical user, can feel that way about Linux, imagine how normal non-techie people can feel about it.
Fortunately, the situation has been much improved in the past few years, and there are at least a few distributions out there that look very good and are very intuitive to use, and most of them use Ubuntu as their core, but with a different interface. However, the apps are still not as polished as they should be in 2012. And I think Canonical has a great opportunity here to start creating design resources for Ubuntu app developers, in the same way Apple has created resources and design tools for iOS, Google with Holo for Android, and Microsoft with Metro.
If they would do that, you'd quickly start seeing highly polished software on Ubuntu and other distros based on Ubuntu that use its Software Center. But before they even start doing that, Canonical has to rethink its user interface, because the UI and design of those apps will have to look similar to the Ubuntu UI. The problem is I don't think the Ubuntu interface is that good right now. I don't find it very intuitive myself, and it's also quite slow, even on high-end machines, while it's almost unusable on ARM chips right now.
So if Canonical is serious about putting Ubuntu on phones and tablets, they really need to create a much leaner UI, that uses much fewer resources, even if ARM chips are getting better and better. Canonical is very serious about support for Cortex A15 and future 64-bit ARM chips, but there's still a lot of room for improvement until they can make Ubuntu run as fast as Android Jelly Bean on these chips.
Canonical also thinks it will take them until Ubuntu 14.04 LTS (spring 2014) to create this kind of optimized version, that will also probably use at least some modified user interfaces on smartphones and tablets, and it remains to be seen how Ubuntu apps will work on these mobile devices.Will Canonical be able to make Ubuntu a powerhouse OS in the mobile world? That seems pretty unlikely right now with Android having such a huge head start, but it certainly can't hurt Ubuntu's popularity in general, which is also what Canonical is hoping for.
They believe that this can only make Ubuntu more popular on desktops, and Ubuntu and Linux in general needs all the help it can get with that. But if they manage make Ubuntu a whole lot leaner, with a lot of polished apps, with many PC games being ported to it, I think it will get pretty easy to recommend Ubuntu over Windows or Mac OS X in the coming years. So that will still be a win for Canonical, even if Ubuntu doesn't get a lot of traction in mobiles.