Well, considering the original game rolled back numerous times in its full release (the last I recall was in 2012 where someone went from level 42 to level 20), I'd say a rollback or two in a beta should probably be expected, wouldn't you say? Things happen that can't always be predicted, the period of the game or how long it's been out is irrelevant to that. Saying rollbacks should only occur in alpha is simply not feasible, and anyone who's in game design, or programming in general, would tell you the same thing.
As for happening again, it very well could. There's no way to predict stuff that could be bad enough to cause a rollback, and it can happen to any game at any time. Even popular games like World of Warcraft could suffer from something that could force a rollback (albeit this would be pretty rare given their resources, but possible nonetheless).
At the end of the day, just enjoy the game, things like this are pretty rare
