To clarify: Based on current trends regarding hardware, e.g. the "post PC era", and software, e.g. "walled gardens"; an expectation that in the future one will be able to run the OS of their choice on common computing devices with the sanction of the hardware manufacturer increasingly looks less reasonable.
Yes, it is possible to boot Linux on an iPad. And it is also likely that one will be able to likewise boot Linux on devices using the new Intel parts.
But this does not make for a reasonable expectation that end users (let alone general consumers) will have a viable practical alternative to do so in the future. In general the trends are in the other direction, particularly in regards to hardware being configured as general computing devices rather than having systems more firmly embedded.
A few years ago, Napster, made it look as if music would be freely distributable. A few years before that, there was no advertising on the internet. Earlier, commercial software was shareable among people who did not purchase it. At one time computers filled large rooms.
Change happens.