So while Vivo has finally announced giving their phones Android 6.0, the JiaYu S3 is getting Android 7!
JiaYu do seem to have been laid to rest (despite rumors of buyouts and new phones) however the Chinese based JiaYu community is still thriving and Chinese devs have been hard at working building new Android builds for their favorite phones.
According to a recent post on the JiaYu Forums, the JiaYu S3 can now be (unofficially) updated to a Beta system based on Android 7.0!
Two builds are available depending on the version of the JiaYu S3 you have and according to the changelog most features are working with the new ROM.
Do keep in mind that this is a development ROM though and there might be bugs before installing it on your own phone. Details and download links can be found here.