I think the reason why WWE is bringing back the Bad Blood PPV this year is that Kane will retire there. It makes sense since he will be running for mayor in his hometown soon so he has to end his professional wrestling career sometime this year. And doing that at the Bad Blood PPV would be awesome because he made his debut 20 years ago at the Bad Blood PPV when he interfered in the first ever Hell in a Cell match between The Undertaker and Shawn Michaels.
My prediction what WWE will do is that they will be doing a storyline between Reigns and Kane where Kane will be retired from Reigns. Makes sense because Kane wants to take revenge against the person who retired his brother. And at the end Reigns will not only be the person who retired The Undertaker, he will become the person who retired The Brothers Of Destruction.