A1C under 6= no diabetes, really.
Once you are diagnosed with Diabetes, it remain with you forever. There is no permanent cure of Diabetes and Blood Pressure so far. I have A1C under 6 but that doesn't mean my Diabetes is cured. If I deviate from my current eating and exercise pattern then A1C will start rising once again.
What you are talking about is the possibility of it coming back. Yes, maybe you will still have partial insulin resistance and this stays.
There is probably no peripheral neuropathy, retinopathy and nephropathy, etc. with A1C lower than 6.
In fact, 5.7-6.5 is usually considered pre-diabetes and below 5.7 is considered normal.