I like the idea tha Ramuh might view the Echo as a threat. It would certainly keep in line with the trend of recent plot revealing more and more about the Echo to us.

I think it's also possible that those pesky Garleans will set him off somehow. They're certainly already invading his domain, and who knows whether or not Ramuh will descriminate where he throws his levin fury?

But if we do have some dialogue with Ramuh before he becomes a threat, or after defeating him, I would really love it. In my opinion, one of the best scenes in the 1.0 plot was conversing with Ifrit. Not even fighting him, but just having this extremely powerful and fearsome creature deliver some plot to you before telling you to get off his lawn before he roasts you alive. Something akin to that with Ramuh would be an even more powerful experience now, since we've only seen primals as enemies to this point.