But there is a limit to everything ?
I just completed conversion of my game from cocos2d-objc to cocos2d-x C++.
And from that I can see now: ideal language for cross-platform development - it's that is supported by "native" IDE's, so Xcode & Android Studio and so on.
So, SWIFT currently isn't supported and who knows when or even will it be? C++ is everywhere...
I'm looking forward when swift will be supported at least for android studio, but currently it's not time for this language as for engine development...
Maybe rework cocos2d to c++ ? Without any problems to be cross-platform and high speed?
By the way, I converted ObjC code of my game to C++ line by line, no additions or removals, like something wasn't converted to cocos2d-x, because it was missed in it or was something new and I used it to improve performance, lets say polygon sprite. No, all was converted as is, just changed language.
And results was impressive. Exactly the same scene on iPhone 6 were loaded: 26-28% in cocos2d-iphone and 17-19% in cocos2d-x. I think thanks to C++. Batching works the same on cocos2d-iphone, if you think that it's not and thats why it got so poor performance and I definitely using same setup(res, device, build type etc.).
So for me, currently it's only one option to use C++ for game engine.
or.. https://news.realm.io/news/swift-on-android/ ?