JSON! yay! ... wait. what's the benefit?
There is a small benefit in that serializing/deserializing components becomes a little more standard.
I have been using custom code for years to populate Delphi or FPC components over a network based on dfm/lfm format whereas I use json for other objects, even in between different languages (deserialize to ecmascript or C++ objects).
So, yes, I can see a point in using json. But it is not that important.
As for SVG support: I'd rather see html canvas support. (I am working on that off and on, btw, nothing publishable yet)