Focus on Existing Expansions
IMHO It is quite ridiculous to even consider any development in newer not yet final expansions. I have seen many post on this/and other thread/s discussing about how good/bad WoD expansion is, its PvP/PvE aspects, or Blizzard's new approaches to the game. It makes me think people are completely detached from reality. The hard fact is that in this server WotLK realms are the ones in best shape and still need a lot of work: basic mechanics like path-finding, PvP instances, or more complex game-phasing need really to be taken more seriously. Not to mention that the other two available expansions here (i.e., CATA & MoP) provide roughly half of their content and have similar core issues that need to be taken care of.
Based on these facts, is WoD dangerous to Warmane? Yes. Leaving Blizzard's legal issues aside, Warmane developers should employ every second of their precious time in fixing the currently available expansions to prevent frustrated people leaving for other servers, which is sadly already happening.
You have my support. I have chosen you as my WoW server many years ago. I really hope you make the right choice on this matter.