I'm more shocked that there is no permanent deputy to take over at least part or most of the role. For an organisation so fanatical about safety where is the FIA's own succession plan for such an important player.
There was until the middle of 2016 (it was Herbie Blash). However, he then took a position as permanent head of marshal training; the heretofore lack of one was at that point about to become embarrassing, the FIA trusted practically nobody else for the job and Herbie (about the same age as Charlie) may well have quietly liked the idea of a slightly more relaxed lifestyle.
There was no obvious successor... ...so the FIA did something that I think was quite clever. They had each track pick a deputy from their own ranks, with a view to giving more opportunities to a wide variety of nations and perhaps help with getting Jean Todt re-elected. So there are 21 people who could have been called upon to step into Charlie's shoes at short notice, depending on which race happened to be the next one after he retired/died. It just so happened that Australia got the sad duty.
It also means that potentially, 21 people could become the permanent head. Mr Maisal did what, to my eye, was a fine job. I'd like to think that increases his chances of getting a key role, because he knows exactly what he's doing. However, the whole "it would take 3 people to do what Charlie does" element means the other 20 race deputies shouldn't give up hope yet. It's also possible a full decision might not be taken until the entire year has gone, so everyone gets a fair chance at "audition" and the FIA has time to split the roles appropriately (if that's the avenue it is going to take).