It can happen. I've seen people go back to becoming alcohol even after a year of sober. It's not complete if we are not able to avoid it regularly for a lot of years. There will always be the urge to gamble again especially nowadays that advertisements about gambling are coming left and right in different social media and even in local television.
It's possible that a gambler who got through gambling addiction will go back into playing because it still calls him.
As long as temptation is accessible to those people experience already an addiction before there's really instances that they might go back.
But some recovered gambler which experience addiction before are in control now, but we can't also deny the fact that some of them are so unfortunate to get back on their miserable or problematic life.
Nowadays we could see gambling ads everywhere and it seems that government find it hard to control especially those illegal casino that's why its spreading so fast and it able to reach to vulnerable individuals.