AFAIK one issue with Skia is that its API is not stable (and it is written in C++ which makes stability kinda hard) whereas Cairo's API has been stable for a long time.
Side note: Skia can't render SVGs directly. You need a separate library to do the parsing and issue commands to Skia. I think they might have experimental support for simple svgs committed in the repo, though.
great, so it has what 18 months before being killed off?
It's used by Chrome, Blink, and a lot of other projects, so unlikely to be killed any time soon.
Skia has been around for 15 years (open source for 12) and is used in a number of high priority projects for Google (e.g. Android, Chrome). It's incredibly unlikely it will be killed any time soon.