So Opera isn’t dropping Presto for WebKit but for Blink, which is Google’s new fork of WebKit that exists, as far as I can tell, because Google and Apple have a hard time playing together nicely. (See this HN thread in which people make various claims).
Meanwhile Mozilla is teaming up with Samsung to write a new rendering engine (Servo) from scratch. One which, from first impressions, is very heavily geared towards mobile devices.
I’m going to have to revise my testing platforms before very much longer, aren’t I?