The problem is, not everyone has a smartphone, and those who do may not have Internet access at the station whether because of reception or credit. There are no PDF versions accessible by the general public and the last time I checked the apps required payment, which then involved signing up. Perhaps I should write a letter to Trains NSW..
I thought your initial concerns quite valid, and I'd suggest that this would be an appropriate course of action. Of course, timetable books are available from station staff (at locations like Central), although these are needlessly disposable options if you only want to look at one train once - a poster is far better! I'd leave official feedback though, if they don't think people are using them, they'll leave them gone.
I'd suggest that you're right in your estimate that they're waiting for a new timetable poster with the new timetable. Seems rather short sighted not to just cover up the old logos though.
The apps don't require payment (at least, not Tripview) unless you want to save your favourite trips. It's free to use as an instant-timetable generator. Transport Info has their own app too, which is basically an app-version of the 131500.info site.
I'm pleased to see that, in true Railpage tradition, everyone has used this as yet another thing to beat CityRail/Sydney Trains/NSW Government over the head with. Honestly, mountains out of molehills, some of these comments!