Also, I think David mentioned using
Unity engine (or maybe some other third party engine), not his own inhouse built engine. I guess too many people asked for all graphic eye-candy they get in todays games and it is not possible (i.e. it is too big of resources hog to be viable) in 2D games like EK.
And yes, I guess it can take about 2-3 years to be developed. EK was developing I think about 1 and a half year before beta (I guess development started somewhere in 2014) and you see how long it actually takes. With very long period with beta versions available to public, first only for Android, later for iOS and finally for PCs of all varieties (Windows, Mac, Linux).
Now David needs to learn how to work with new engine, but at least he doesn't need to learn how to code it (which I guess is much easier task

).
EDIT: David wrote his answer before I wrote mine.
