If I'm not mistaken last years christmas event only had a x3 xp bonus but had no loot bonus, and probably older versions too.
Based on the fact that halloween was a complete failure coming from BB, the many bugs that appeared and assuming more bugs will come before or during christmas event, I suggest that this years event should have at least x2 bonus loot xp if not x3.
I consider this is early and players should have plenty of time to vote and BB should have plenty of time accepting it and implementing it.