As an ALL Gold for some years, i don't think i've ever had a room upgrade.
That may be down to the properties i typically visit (generally Mercure/Novotel), but even when asking at checkin about it i've always been told "no availability".
That includes times where i can see on their website that upgradable rooms are bookable (a few hours earlier) and challenged the "availability" still i get the same response.
I wouldn't bank on any upgrade at all and book the room i needed.