Elewa isn't going to go "evil" at least not in a conventional sense. You won't see any moonbase lasers or death camps from him.
He is however going to conduct himself that people might not agree with. As shown with Takeshi, if he deems that you're not someone he actually cares about then he's totally okay with using people to achieve the greater good he's aiming for. He's become a lot less afraid of authority and much more ready to challenge it if he finds it wanting. He's not that big on empathy because he still doesn't fully understand people at large and he's become quite stubborn and convinced of his course so he's going to be hard to dissuade. He's still a pacifist but he's come around to the idea that sometimes you might have to kill someone in order to stop them.
That said, it's hard to tell. A lot of his character direction is going to be informed by what happens to us throughout the remainder of the game and how his interactions with other characters go. I'm not planning for him to end up as a supervillain but it is a minor possibility.
For future projections; his main course of action when we get back into Eden is going to be heading into Sector 12 to start organising and securing the people he cares about and trying to limit the loss of life in the ensuing chaos as much as possible. From there he'll send his brother into the Scoop and Sector 13 and start moving inward, trying to keep everyone safe. First and foremost, he wants to keep 'his people' safe and right now 'his people' constitutes the population of Eden.
I'm also looking forward to the day when he and Max talk about economics.