Nobody has done it fully yet, including Apple. But again, Cringely doesn't give a single reason why Apple would succeed in this space over Google or Microsoft, or something like Ubuntu. Enterprise is probably going to want to stick to mostly one OS if everything has to be ported over and all their accessories need to be compatible, and iOS is very very unlikely to be first choice of most IT departments for obvious reasons.
So the idea of convergence isn't new, and the idea that iOS would win at the convergence game in the Enterprise is implausible - I don't know what he was smoking when he wrote this article.
Enterprise is going to be a slow-adopting beast, no matter what, but that doesn't mean that iOS (or some future evolution of it) is out of the running. Come on, you're not really saying that office work can't ever fundamentally change again, now that PCs are here -- are you?
Firstly, iOS as it stands is very very poor compared with a desktop OS for office work. At an absolute minimum people need to be able to have two documents up on screen at once, maybe one spreadsheet and one PowerPoint doc.
Secondly, im willing to entertain the idea that iOS could evolve into something that could become useful as a desktop replacement, but i am yet to see a single reason why it would have an advantage over competitors, and there are many reasons, such as cost, that they are at a disadvantage.
From my experience of working in an office with admin teams, the very large majority worked with apps open on the full screen and tabbed between them. Very rarely would they have more than app visible at once, even when they knew they could they wouldn't.
That has not been my experience with office workers. They often work with one maximized app, but they often work with more than one document at a time. For admin teams in particular they often have a small chat client open either for work reasons, or more commonly to chat with coworkers.
So the idea of convergence isn't new, and the idea that iOS would win at the convergence game in the Enterprise is implausible - I don't know what he was smoking when he wrote this article.