I have no knowledge of the hybrid or backbone, but knockout is open source and has a significant mind share. If it did go away, it would be for something as goo

I have no knowledge of the hybrid or backbone, but knockout is open source and has a significant mind share. If it did go away, it would be for something as good or better that existing apps could port to. If you didn't port you could fix any bugs yourself; I don't see that as more difficult than implementing the library's features yourself.