It will indeed be interesting to see if that happens. If I was to bet on it I would say that it's not going to happen in cinematography. Indeed moving focus through the scene is one of the tool that a cinematographer uses to achieve the desired artistic effect. It is hard to imagine that a computer algorithm would be able to predict how fast or slowly we want to bring objects in/out of focus and how much smoothness we want in these transitions.
That's an interesting question, and you're right that for that particular effect, you're probably better off doing it manually—preferably with a long-throw manual lens and a reasonably long stick attached. But that's likely to be an occasional thing, with either static focusing or traditional subject-following focusing used for probably 99% of your shots; if you're using focus to move from one subject to another for 99% of your shots, the viewers are likely to get nauseated rather quickly. :-D
Can autofocus beat the precision of a measuring tape?
Depends on how narrow the depth of field is. At large f-stops (e.g. the Zeiss 50 f/0.7 lens that Kubrick used), it can be done by hand, sure, but if you blow that up to where you can see pixels at 4K resolution, you're almost certainly going to notice the softness compared with what modern electronics could achieve, particularly if the subject is close to the lens and he or she decides to move a fraction of an inch. Mind you, that's a rather extreme case. :-) At more sane stops, it's not quite that bad. It's still a lot of work, though—work that's largely unnecessary with a decent, modern, subject-tracking AF mechanism (even without eye tracking to set the starting point). It's not that focus pulling can't be good enough, so much as that the extra work to make it good enough is significant, and it makes little sense to bother with that when a simple circuit can do at least as good a job (if not better) without all that effort. :-)
Lastly focus depth even though sometimes shallow isn't nil in most circumstances so small focusing errors might not have an adverse negative effect on the result.
That's true. With that said, the higher the resolution, the more visible that small effect becomes. At some point, you start to swear because the soft focus limits your effective resolution, and all those extra pixels are just taking up more space on disk without any real benefit. I'm not quite sure where that magic point is for manually focused movies—you'd have to ask somebody who regularly does film scanning and media ingestion for their take on it. Obviously it would depend on the f-stop, the distance to the subject, the film format, the focal length, and the skills of the person doing it. :-)
Chances are you've got the experience here while I certainly don't. However my impression so far was that what you're saying is true but not to such an extreme extent. People do use old lenses including those which are much older than a decade on modern still cameras and the results they're getting certainly don't look like they were shot with resolution of about 1/3 mega pixel provided by 720p video. I think the truth must be somewhere in between and the old glass must still be a valuable tool. After all if that glass was indeed that bad why wouldn't the prices not be nil today? Some of these lenses still command amounts of money which one on a budget would think twice before spending.
I'm probably being a bit on the cynical side; I'm sure there are some older lenses that are usable at 4K. The point I was trying to make was that the newer lenses are breathtakingly better at high resolutions—maybe not at 4K, but long before you get to 8K. And their handling of bad lighting conditions (lens flare, for example) is just amazing compared with the older lenses. Unless, of course, you're into that whole lens flare thing. (Yes, I'm talking to you, Mr. Abrams.)
BTW, 720p is just shy of a megapixel, not a third of one. You're probably thinking of the old 720x480 format used for widescreen standard def content. :-) Not that a megapixel is all that amazing, either, mind you.