Yes it is being tested. Has been for a while in different forms. No station really wants to bite because (IMO) if they do grab onto it then the excuses to limit the amount of radio stations (i.e. competition) on the dial will become less.
Conspiracy theory!
For real though, yes it is being tested (by 94.7 amongst others) and there will soon be a station broadcasting into SA on AM in digital format. But I am sketchy on who, what and where or even when... But it could be before the year is out...