I'd love to stay with Corona, having used it since 2010 and just about to re-release an app and build a follow up on my same platform. But, if I have to move it's looking more and more like Unity 3D might be the way to go for the following reasons:
1. Stable company
2. Diverse platform support
3. Large developer community
4. Standard programming language (C#), not a proprietary language
5. Reasonable cost
I'm not so concerned about it being overkill.
Please feel to chime in with your opinions. I think we all need to at last consider all our options.