I don't know why, but ... I think they could get RVD to rejoin Kane.
Yes, RVD has not storyline atm because he has a short-term contract (or so we hear), but I imagine they could extend his contract if they find a suitable story arc.
Kane by himself vs the Wyatt must either end soon, with the Wyatts moving to something else, or allow more characters on stage, to help Kane. Big Brother Undertaker would be lovely, but a bit early (and we should expect 'Taker if/when he comes back, to focus on a single match for Wrestlemania).
Kane could be "turned" by the Wyatts, for a while, and there would have to be someone able to bring him back (and eventually betray the family). Bryan would be a good candidate for that role, but he's already engaged with his own main line, so.. RVD could fit that bill?
Thoughts? I know, I'm just being an armchair writer....