8kVA was certified last month. Inside track says 15kVA comes end of September if there are no surprises, which there should not be.
That is good to know.
What about the 5kVA model - which is what I have?
I have no idea. You have to ask the sales people that, they drive that process.
It is also possible the Quattro-II might be first.
Mine is the Quattro-II 48/5000/70-50/50 to be exact. How do I get hold of the sales people? Is there anyone in particular?
The shop/guy you bought the inverter from is supposed to be the first line of support. Otherwise, look on Victron’s website for the South African reseller’s address, it is there.
Jaco? 
I see there are a few more with the “certificate valid until” column filled in. Some Goodwes and an Ingeteam too.
The unifying property seems to be that those with expiry dates listed were all done by either Dekra or SGS. In the case of Dekra, it seems they started doing this later.
So… it is likely because the 8KW and 10kW was done by SGS and not by Primara, and that’s just how SGS writes their certificates.