what are the long-term options for ios & c2?
clearly cocoon is not really the best option.
are there any other free & promising options in development like CrossWalk for android ?
Crosswalk is ok for android, but many have seen performance problems with it, up to 50%. When I tried it, my game was unplayable. And that is after a long optimization process to get it to work on CocoonJS (removing physics, moving code, reducing sprites, etc)
CocoonJS is the best solution I see so far, but it is left to be seen if they will keep developing it. They said they will release once a month, but that has turned out to be false. 2.0 is coming out soon, but who knows if that will have bug fixes or just new stuff.