Sweetie,
No, it doesn't necessarily mean a downward spiral as long as you look after your general health and keep your BGs under control.
I had gestational D during both pregnacies, and developed T2 when I was 33. For 30 years I controlled by diet first, then gliclazide (which exhausted my Beta cells) and now, unfortunately, by insulin. I don't have any complications AT ALL and I'm now 63!
That's not to say that something may not be lurking round the corner, but I'm doing everything I d***d well can to load the dice in my favour.
I've (nearly) always paid attention to carbohydrate intake to stop huge rises in BG. These forums have been marvellous for me - I can't imagine why I hadn't been here a few years ago.
Barb