Sure, all that makes sense, 'the only computing device they will ever own in their life is a smart phone' is simply not accurate, though. What you really mean

Sure, all that makes sense, 'the only computing device they will ever own in their life is a smart phone' is simply not accurate, though. What you really mean is that the only computing device they have owned so far is a smart phone. You can't claim that in multiple decades smartphones will be the dominant computing platform. It could be anything; AR goggles, brain implants, hell, we could have gone back to the stone age and be mucking about with abaci. ;)